Far be it from me to discourage solar (I've had panels on all four RVs we've owned over the last nearly 20 years). But 400 to 500 sounds like much/all of the roof would be covered.
With your current 10 gauge lead-in you are limited to probably 400 watts (unregulated panels can run to 18 volts, time 30 amps... roughly 400 watts)
A good resource is
RV SolarPersonally, when boon-docking (summer time) we don't watch TV, we have LED and florescent lights, are careful with power and find that 100 watts is enough.
