keyless remote issues

I have a 2001 Chevy Cavalier and it came with a remote that is getting old and I used to own a 1996 GMC Jimmy so now I have that remote can I reprogram it for the Chevy? And one last thing I also have a remote that was for a 2006 Ford Focus, can that one be reprogrammed on the Chevy? If I can do any of these please explain how.

You definitely cannot program the ford fob to work on a Chevy. What you want to look at is the FCC/ID on the back of the original fob if the new one has the same than it can be used. I have bought them on eBay before and they worked fine just type the FCC/ID and fob into the search engine and there you go, I got a pair for my Aurora for like $35.