It sounds like you're looking to do a simple camping conversion.
If you want to charge phones, then just get a few adapters like these
and hook them up to your solenoid(positive) and your bus frame (negative), also you can get a surge protector and an extension cord for when you're parked. You can get your phones charged while the bus is running, or plug it in when someone plugs you in and you can leave it at that.
I don't know specific of how to keep it road legal, but I believe ditch the yellow, stop sign, flashers, and keep it under 26,000 lbs. You should also read about how to use airbrakes, I can't tell you if you need a CDL to drive with it. But I don't have a CDL, I think weight is more of an factor than the air brakes related to the CDL.
Call around insurance agents, you'll likely have better luck with small insurance companies where the agents get commission to sign you up with big companies then going directly to a big company (say progressive or national general). When I had my bus insured, I got it insured as a food truck at around $100 a month. Whatever it takes right?