I would change the oil in both the generator and the drive engine. Cover the tires to keep the sun off. If you do not have a roof vent cover similar to the Max Air you may want to consider installing a couple; this will allow you to get some air flow through the coach and not worry about rain getting in. Make sure all batteries are full of water and charged and when you leave disconnect a cable from each bank to prevent full discharging. You will probably loose 30% but should be ok once you recharge them. I am sure some others will think of some more to help you out with this storage. Good luck and be safe.
Mike, RVIA & RVSA Certified Master RV Technician
Amy, Dr. Assistant - Roxie & Mei Ling, four legs each
2000 Gulf Stream Scenic Cruiser 450 hp & 1330# torque
06 Saturn Vue, 06 Chevy Z71 4x4 & 2014 Corvette Z51 M7