97 Audi Cabriolet Auto Trans problem?

New to Audi, couldn't resist this great looking car at an auction, even though it had a slipping Trans and a non-working top. After driving it, I like it even more.

The Top was difficult to open at first, would get stuck half-way open and not go into the well (had to push it). Closing the top worked fine. I use the top a lot (weather here in St. Louis has been great), so the problem has become intermittent - sometimes it works perfectly. Is it possible the previous owner did not use the top very much and this problem will go away completely?

The Auto Trans is the main issue now. In "Drive", it slips going into each gear, "Reverse" is slow to engage. Driveability is better if I shift manually (1,2,3,D). Engine light comes on for a day or two, then goes off for a day or two - P0740 Diagnostic Code (Transmission Torque Converter Solenoid). I took it to a local Auto Trans shop and he did not even know how to spell "AUDI", but was willing to start working on it if I could leave it. Took it to an Audi dealer and was impressed by their knowledge and professionalism. After a $160 Diagnostic (where they check the complete electrical, mechanical, hydraulic systems) they will provide an estimate to repair. He said repair costs could run from $200 to as high as $2000, if the repair takes over a day a courtesy car is privided free.

I am currently driving it as is, and searching for information on the Transmission Torque Converter Solinoid, i.e. Part #, cost, location, installation instr, etc. If this part is not too difficult to change, I would do it myself before taking the car to the Audi dealer. So far I have had no luck finding repair info - any suggestions?

Thanks,