I like this thread title "Be easy on me". Haha.... do people think posting on a forum is like a war zone?
There will be a lot of work done to NES right around the time we get more NES lovers probably!

Most of the games would work already, I would guess the compatibility rate is over 95% for NES as the emulator is cycle accurate. However with the issue of bad .NES headers, the massive game library, etc, it is hard to gauge exactly.
Since the .GAME format will be coming along and replacing the .NES format it will take a little time to handle all that and get the database done. It's a massive undertaking and I'm not bothering with it until the core stuff I've been talking about for 2 years now is done, which will be over the next few months.
As to mappers, croser, head over to :-
http://wiki.nesdev.com/w/index.php/MMC