hi my car has done 57,000 miles it a cento 2002, i would liekt o know has any 1 changed a cam belt on there car? and is the timing marks a problem, is it tricky job cause my friend and i said wel have a go save us some money or is it wiser to go to garage, my friend is a mechanic just never changed one on a cento before, any tips please or advice would be much appreciated thanks aaron

Easy enough..
You need to jack up front and take drivers wheel off and inner arch to get at it. Slacken the bolt holding alternator in place and remove the belt. Then the tricky bit, getting the plastic cover off the cambelt, can't remember where all screws are but they obvious enough, just getting it out is fiddly, you just must persist. Iirc it is in 2 pieces. Once off, slacken the tensioner from the belt and remove, and replace in everything in reverse.. You must change the tensioner too, last time i bought a belt it came with one but not all do

Hope that helps, took me 20 mins on my own when i did mine. If you not got one, go purchase a haynes..

Oh and why not take pics while your at it and write a guide for the guides section

Theres already a guide isn't there? It's just pictureless IIRC.

Here and here.