I dunno, A35's are much more complicated than E50's. I wouldn't recommend cracking the case unless something was FUBARed you were SURE that you would solve things that way.
On my A3 at least, (and I believe that A35s fall under the same principle) you can replace the seals without cracking the case. You have to take the clutch cover and clutches off, but that's not that hard. It's kind of a moot point though, because if your crank seal was bad, you'd be burning transmission fluid, and there would be copious amount of white smoke coming out of the exhaust. If you aren't seeing abnormal amounts of smoke, then your seals are probably fine. Another sign of burning transmission fluid is if you refill it to the proper amount, then check it later and find you have significantly less fluid than you started with, but you know it hasn't been making leaky transmission puddle fluids on the ground.