The answers to most of these would depend on the specifics of the conversion; I suspect different conversion companies do things in somewhat different ways.
I would not expect a lot of insulation. There's not a whole lot in most RV walls, and probably less in a shuttle bus. It may be about on par with a typical RV if you're lucky. That's mostly guesswork on my part; I don't have direct experience or specific knowledge here.
Moving the rear heater probably wouldn't be overly difficult; it would presumably involve rerouting or running different hoses from the engine (and wires for the fan). In an RV it would be of less use than in a shuttle bus since frequently when one wants heat in an RV you're parked for the night or day.
The roof air conditioner I suspect would have an engine driven compressor, in which case it couldn't (practically) be converted to operate off of shore power. On the off chance that it's an electric air conditioner and there's a generator to power it (or a large inverter and a large alternator on the engine), conversion would be trivial--just powering the circuit from the shore power system.
