You can do it yourself without much trouble at all! If you get stuck or unsure half-way through then the forum's always open. I got my kit from shop4parts. Consists of a tensioner bearing and belt.

I had to however get the belt changed as there's two pitches you can get. My engine was the lower pitch of the two and I got sent the higher one. Easiest thing to do is go to your local FIAT, give them your chassis number and they can give you the appropriate kit. It's around £20 I think.

The job took me, well, it took me a few days but that's because I was waiting for the correct belt, but actual working time I would say no more than 2 hours. At first I thought, no way could I do a cambelt, but after a thousand miles it's still running perfect! You can too!

May as well do the alternator belt while your there too, it comes off anyway.

In the way of tools, a spanner set (for alternator), torque wrench, 7,8 and 10mm sockets (for various parts) will be pretty much all you need. The torques will be in the Haynes for the various parts. May as well replace the tensioner bearing nut with a nylock nut when it's off, can get that from any DIY store.

Disconnect the battery, chock the wheels and jack the drivers side of the car up, whip the wheel off and support on axle stands (the car, not the wheel). Remove the arch liner, there aren't any hidden nuts so just remove all the one you see and it shoul be free to move. I couldn't actually fully remove mine (although I'm told if you tug hard enough it does come out) so I just bent it and used the disc/caliper arrangement to hold it back. Now you can see the rabbit (you are the dog). Working from the top, take the top belt guard off, (mine was held in by one bolt on the back of the head). This forms half of the cover, the bottom part will still be held in from below. Now, working from below, slacken the alternator nuts off with a spanner. Slide the alternator toward the block to make the belt go slack. Remove belt. Now, undo the three bolts holding the crank sensor pulley (the pulley the alternator belt went around) on. Remove said pulley. Now you can undo the bolt holding the lower part of the belt cover on, and remove it and the cover.

The new belt comes with two seperate white or yellow lines, simply have to make these correspond with the marks on the pullets. Before you take the old belt off, turn the engine over to TDC on cylinder 1 by lining the mark on the crank pulley with the mark on the engine block, pictures of these marks are available in a sticky thread in the Punto tech section.

Slacken off tensioner bearing and remove belt, be careful not to move the top or bottom pulley now (don't worry, their not very easy to move, and won't rotate by themselves), the water pump pulley can be wherever you want it.

Change the tensioner bearing by fully unscrewing the nut, and sliding the bearing off the stud. There are a further two components for the bearing (which will come out when you take it off), but these will be straightforward to refit just by looking at them. Refit (with the nylock nut if you so desire). I couldn't get a torque wrench up there, but 28Nm will be sufficient (basically not much at all). Don't tighten the nut just yet, still have to get the new belt on.

Thread the new belt back on around the pulleys, making the timing marks on the belt correspond wth the marks on the pulleys. Trust the markings between belt and pulley, more than the markings between pulley and block. If you have fitted it correctly, the timing marks will both line up exactly, don't stop until they do. To help me see the marks on the belt, I tippexed a mark on the side of the belt (where the timing mark on top is), so I could see side-on where the mark was.

Now, using a suitable instrument (I used a spanner), lever the bearing (against something solid like the block) against the belt, until you can turn the belt through 90 degrees (comfortably) at the mid point of the longest part. You shouldn't need freakishly strong fingers to turn it through 90 degrees. It's easiest to get a second set of hands to maintain the pressure on the tensioner, while you feel the belt and say "a little more", or "a little less", to the second set of hands. Then, tighten the tensioner bearing nut to the torque described above.

Now, using an appropriate socket, turn the engine over (using the socket on the centre bolt of the crank pulley). It will be easier to do this with the plugs out. Turn the engine through 2 complete revolutions to check that there are no obstructions (shouldn't be anyway if the timings out as it's a safe engine). Refit the crank sensor plate (toothed golden circular thing), noting the hole in the plate lines up with the pin in the crank pulley. The torque (off the top of my head) is 62Nm. The alternator belt doesn't need to be on just yet, we're just making sure the engine runs. Re-connect the battery, refit the plugs (if you took them out), and make sure the engine bay and especially area around the belt is clear from any tools, parts, etc. Now try and start the engine. It should fire and run just like before, if not better. You don't need to do a prolonged test, just see if it runs ok, then turn it off - don't want a flat battery and a hot engine to finish the job with!

Now take the crank sensor plate back off again, and refit the plastic belt cover (maybe you can get it back on with the pulley in the way, but it would be waaaay easier to just take it off again). Now refit and torque it correctly.

Fit a new (or the old) alternator belt between the two pulleys, and again, using a suitable instrument (and/or a second set of hands) , lever the alternator out to make the belt go taught. Tension so that you can push the belt down (or up if you want) 5mm with firm thumb pressure. Now tighten the bolts with your spanner. Good luck in getting a torque wrench up there so I just did them up tight (you should be able to gauge what is right when you slacken them off in the first place).

Refit the top end belt guard/s, then refit the arch liner. Et voila, reconnect battery and away you go (after refitting the wheel, lowering the car to the ground, not before taking the axle stands away).

This is for an SPI Sei however, I believe yours may be MPI. It isn't all that different. Think I also heard the MPIs are a little tight for space under there too. I think you may have a crankshaft sensor of some sort on the top end, should be intuitive to overcome these differences.

HTH

Fix it yourself, learn something and save money!