If that's all they found on a 15 year old coach you are doing great!
For HWH air leveling parts contact Paul at AZPETE on the Irv2 forum. He works for HWH and can answer your questions. His email
ispfmaddox@att.net and his phone number is 602-549-3638. He is a Commercial Member and has posted that his phone is always on, and if not answered, leave a message.
Most of the rest of your parts are available from any heavy truck/bus parts store including NAPA.
I think something got lost in translation for this part:
Front Drive differential oil lead on input seal.
You have a rear differential (not front) that faces the rear engine/trans. Do they mean the pinion seal is leaking? If so, again it's available from a heavy truck/bus parts store.
Just a suggestion. There are some very good repair shops in the Phoenix/Mesa area. I would ask for suggestions from other IRV2 members in the area.