sorry i can't answer most of your questions other than your last one...
yes, a coupe (2dr) OEM radio will work. the only thing is though that it will ligth up orange-red, instead of the sedan yellow-green. If you are needing to replace it, just give a quick look around for the SE civic radio (MP3/WMA, 6-disc, and AUX imput.

I found one on ebay for $100 shipped

) only thing is that it was from a coupe, so lights up orange-red...
here's one now!:
http://cgi.ebay.com/ebaymotors/OEM-H...spagenameZWDVW