Best place to look would be a haynes manual, you know the cylinder head will have to come off. It is very hard to do it with the cylinder head on, although it can be done it is alot of hassle and you need a special tool.
The trick is to pressurise the Zylinder by a modified spark plug hocket to an pressure air hose.That keeps the Valves from dropping in the cylinder..
Once the cam shaft is off., you can unmount the valve seals.
Note that there is a special tool for that .
But you might be successful with something else.
Oil the new seals an press them on the seat. Use a plastic hammer an some
circular formed tool to push them in the right position.
Good luck !
Get the head and the valves to an engine shop then.
Have the valve seats machined to the modern three angle seat.
They will also machine the valve sides for optimal fit.
It´s about 120 € but worth it. you will have better performance also.
I am trying to get my car up and running its been idle for a while now. Guess after this its the end of the road for me here with FiatForum as i am selling it my little uno.
Would like to say thx to all that have been most helpfull with advise it has helped me alot.