Will,

With question # 1 I did similar things with older VW vans, used fiberglass and
a little construction glue to hold it in place.  My inclination is to avoid
any solvent-based insulations, since the bus is a very small enclosed space
and the likely-hood of toxic effluents having an impact is rather high.  It
did make a very notable effect on the the interior noise, wind, vibrations and
engine roar.  Joel has mentioned some high tech sound absorbers in earlier
posts, 3M materials which are quite costly compared to fibreglass pink.

I "don't know from nuthin" about transmission fluid as an injector conditioner!

Incidentally I have memories of an experience in Billings summer of 1989 when
I had to have a brake caliper on my late great '73 bus replaced.  The good
people at the Metric Wrench who are very knowledgable VW people helped me
through that interesting experience.
Good luck on the conversion!

Ted Hoekman
St. John's, Newfoundland