New Stereo

That's large..not automotive size, automotive uses std sizes ,single DIN ( approx 6 & 5/8" by 2") or double DIN, same width, but double is twice as high

I replaced our dash stereo with a Sony AM FM CD MP3 $79

Do you really need AM/FM? A portable Bluetooth speaker paired to a smartphone or other portable digitial media player may be more useful. I looked at replacing my TT's radio for a number of reasons. I really like the Pinoneer 2700, but it would have still utilized the poor sounding speakers. I ended tryingthe Sharkk speaker about a year ago. It has been great. Sounds better than my TT speakers. I have listen at the campfire, at the beach, all around the yard at home. My wife uses it almost daily from kitchen to bathroom. I wish I'd spent a little extra on something like the Roar now.

RV stereos seem to be no-name import junk. I like Sonix Electronics for their prices. I don't have a radio/DVD to suggest but here is a good install video. You will probably need a bypass kit to trick a car DVD unit into thinking the vehicle is in park to get the DVD player to work all the time.

Ceutchfield.com is a good starting place.