1: Buy true deep cycle batteries, the combo deep cycle / starting "marine" will not offer the performance or lifespan.
2: Inverters: Buy a good quality, name brand inverter. Something that offers true sine wave, the cheap inverters are not efficient and can do weird things. I had one customer that had a cheap inverter and it made the picture on his TV green.
3: Solar panels: Again, buy name brand, and get a solar controller. Consider portable panels, as shade reduces output considerably.
A good sized charge line is a good idea, but remember unless you tie into your truck's charging system via the voltage regulator (not recommended, very complicated and your alternator is probably already near capacity) all your 5th wheel is going to get is partial charge. Your coach batteries wont get a full charge.