2003 cavalier valve replacement

This could be much worse than just a bent valve. Usually a bent valve means a broken piston as well. Sometimes those broken pieces can wreck a cylinder and a head too... Best case scenario you're looking at several hundred dollars. I would estimate parts, head gasket, intake gaskets, belt, head bolts, valve, at around 200.00. Labor would be something like 6-8 hours at local rate, which has climbed to around 150.00 per hour. This would put parts and labor at 1100.00 to 1400.00.

I would be really surprised if a piston wasn't broken or cracked which would add much more to the repair costs. At that point I would do a rebuilt engine.

You could tear it down yourself and check out the damage, but keep all the parts sorted as most shops don't like having a puzzle to put back together, and it will add to your labor costs later. If you have a digital camera take pictures of things so you know where they all go.

Hi:
I am guessing that your Cavalier has more than one bent valve due to the timing belt breaking. It is the problem with interference engines, such as yours, which means the valves hit the piston if out of time. Most cars have at least one valve per cylinder get bent, but sometimes only 2 out of 4 too.

To answer your question, if you are handy, you can remove the cylinder head yourself, and have a local machine shop freshen it up and replace any bent valves, and you reinstall it, with a new head gasket, you should be able to get everything done for $250 or so, unless the head requires machining. This is just a guess, as I don't know the shop rate in your area, and you might have to adjust a bit