I couldn't really find a related topic, so I hope I can get an answer:

I have a 2000 Audi A6 2.7T Automatic(although I can switch to manual) and I've had a recent problem. About a week ago, I was using the manual feature, I was in second gear and I accidentally pushed down which caused it to go to first gear(which I didn't even think it could do) so then my dashboards PRND321 Highlighted in red and the check engine light came on. I can Still run the car and drive it in this condition however, but when switch to Reverse, it shifts really hard(doing some reading, I assume that's because the car is always in fourth gear). Thursday I'm going to take it to my friend who can diagnose the car for me, I was just wondering if anyone knows what it is offhand. I assume due to my reading it's a TCM problem? I've tried some minor tricks of the forums like the reset thing(if I was even doing it right) and disconnecting the battery and such with no such luck. Can I get a price on how much replacing the TCM is if that's the case scenario?