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Question: 2.2L Ecotec Valve Question

I have an Alero 2002 with a 2.2L Ecotec, had the timing chain break, it's obvious now with no compression there is valve damage because it's an intereference engine. I Took it in anyway to have it looked at, the mechanic wanted 2,000 to replace 6 valves I believe this is a job I can do myself, I've been working on cars for a while. I replaced the timing chain myself and practically gift wrapped the car for him to look at, removed the valve cover, etc.

To be clear, if I take the head off and order some valves, is it possible I may not need machine work? shouldn't I just be able to replace the valves, do a leak test on the cylinders, get a new gasket, be sure the bolts are put in the exact same place, line up the cam marks properly for the timing chain, set the motor at top dead center lining up the timing chain mark at the camshaft?

It's my understanding I may not have to send the head out, as long as I verify the valves are properly installed, there are no leaks and using a metal yard stick to be sure the head isn't warped. Remember this is from a car that was running fine 2 weeks ago, just the timing chain broke and some valves are damaged. Shouldn't I just be able to replace the damaged valves and as long as they seat properly as I said and a leak test (Using water or brake cleaner) would ensure it's proper?

Any help would be appreciated. Also do you recommend even though the engine isn't running to put anti-freeze in the motor still. Any suggestions until it gets warm enough outside to work on it, winter is approaching.