2001 A6 2.7T Quattro tiptronic.

Ok, about a month ago I noticed that my shifter will no longer go into 3rd and 2nd. It manages to go into 4th but doesn't feel right, its like something is blocking it (like a Quarter fell in there or something, but I couldn't see anything inside)
I didn't care much because I still have tiptronic and never even use the other gear modes.

BUT now, my transmission went into limp mode. I cleared the codes and the symptoms are that 4th and 5th gear completely slip. 3rd sometimes goes in with a bang if I'm going too slow (like 15mph or so). And if I drive in D it will obviously go into limp mode again if I drive over 20mph because it will try to go into 4th and 5th and they will obviously slip.

Anyways.
It it possible to change the transmission fluid properly without being able to go into 3rd and 2nd gear?????
The whole problem is because I put mobil 1 transmission fluid and its been slipping in 4th and 5th ever since.

What about the shifter, is it fixable or even changeable without removing the transmission?

 

I think I know what it is. I had to change my rear o2 sensors, and the extra wire was hanging around so the mechanic zip tied them all over (yea, I had to use a mechanic because it was a last minute thing to pass inspection and I didn't have anywhere to lift my car myself). I'm betting its zip tied to the shifter cable or linkage somewhere. I'll have a look Monday I guess. But I'm betting it wont fix the slippage, I definitely need to change that transmission fluid, if only it was a 1 man operation I'd have done it a while ago. I need to get my wife to sit in the car and shift gears while I fill-her-up, lol.