long story short: I put both a quart of ATF type F and a quart of ATF
Dexron III in together, one after the other, this evening. Both were
Chevron fwiw. How fast will that cause a problem?  Is just sitting in
the gearbox going to do damage?  A short drive ok? (I can't drain
tonight, and have no other wheels this weekend so either have to bike
six miles or drive to town to get replacement fluid)

How much flushing should I do?  Any special recipes? What's the best
fluid to put in (though as the thing is failing, maybe cheap is best)

The longer version: The transmission's been a bit noisy for a few weeks,
specially in 1st and in neutral. A local tranny shop looked at the
transmission a few days ago, said it had been leaking and they'd
tightened the gasket bolts, but they thought it was ok.  When it was in
their shop a pushrod tube which had just been replaced came loose and
spilled a lot of engine oil, so they probably just wanted the van out of
the place -- I can't imagine that they actually did much.   Even after
adding almost two quarts the fluid level is just on the dipstick mark
(warm running engine in neutral on level ground.)

How far does a noisy auto transmission go before total failure?  I also
have an oil leak from the engine, so presumably should combine the two
jobs to avoid pulling the engine twice, but need to save up a bit before
buying the AT.  Any recommendations on a good place to get a rebuilt
tranny would be helpful.

It's an '81 Vanagon, 90K miles; engine is a rebuild with about 10K on it
(the van had sat for several years, and the original engine was bad
after restarting, maybe because it wasn't properly lubed before firing)

thanks for any advice
somewhat rattled
Alan