1995 auto trans problem - The BMW 5 Series (E34) Lounge

Hello all
In April, I got my wife a 1995 540 i (v-8) auto trans.It's got 140K miles on the trans,& a pretty new factory rebuilt engine.I got the car through a friend who serviced it for the previous owner for over a year (he's been servicing BMW's for years). The automatic transmission has recently had the fluid and filter changed.

The PROBLEMS both occur in Automatic Drive (2):
l. During mild excelleration, cruising at about 50-50 mph, the transmission sometimes continues upshifting and downshifting. The only way to avoid this phenomena is to not travel at the speed where the continual shifting occurs.

2. When the accelerator is floored at moderate (60-65mph) speed the transmission down shifts to the next lower gear, but when I let off on the gas the trans does not easily upshift again. Instead, it stays locked in the lower gear, even without excelleration, for 15 or 20 seconds, until it decelerates to a much lower road speed.

I used to service automatic transmissions in GM cars (in the late '50's/early '60's !!!) and the first problem would have most likely been corrected by a band adjustment. The second problem would probably have been caused by a govenor malfunction that synchronized load and road speeds.
My friend/BMW mechanic tells me that there are no adjustments on this transmission and I have read that automatic transmissions on BMW's get "iffy" over 100,000 miles. I would surely appreciate it if anyone has any ideas about what might be wrong and what might mitigate these problems.
Is there any further investigation I can do before looking into having a new transmission installed? What is the approximate cost? (Do I really want to know the answer to that question?!)

Thanks!