Cathouse: first of all, WELCOME to the assylum...
You might want to just start a thread with your question, more people would see it... on the other hand, there are many many many threads throughout that address the various issues with airheads. Do a search. The 90/6 is, by coincidence, considered one of the very best of a very good line of bikes. They do have their foibles, yes, but there are a lot of bikes still running around, with very happy owners and riders.
The reference above to the MAX BMW fiche will show you that yes, parts are very available.
I like dealing with Hucky's Spare Parts
: Hans is a great guy, good parts, excellent knowledge and service, and as good a price as anybody. His website is helpful in that there are pictures of the various parts, which for me is a real plus!
Anyway, enjoy the madness. Great bikes, great bunch of guysngals on ADV, and help is readily available. So are opinions.