I don't have any experience with VW automagics, but just last weekend I
finally got around to changing the fluid in my similar era high-mileage MB,
and the nasty slipping symptoms I'd been experiencing went away.  I switched
from an unknown fluid to the Dexron III replacement; Chevron MD-3.  I'm very
happy with the results.  I'd also change your filter while yer at it...

--
Casey