Gearbox problems

[Fast at]

Previously had 99 facelift s8 d2 gearbox failed as I am in Spain it was difficult to get it sorted while searching for a replacement I found a mint 98 car for not much more than a gearbox replacement.
Now this one only has 100000 kms with service history ,but the gearbox is running lumpy could it be oil and filter?
Does anyone repair these boxes to last?
I hold on in there I am a huge fan of these cars and I've had a lot of high performance cars