Hello everyone i just purchased an 92 lsi for $3400 and 125k miles

I have read about the 3 great problems with this car:
1. Rear bushings(mainly rear but happens in all 4)
2. Tranny (overheat - install tranny cooler
debree - cloging the narrow path in tranny requiring
an external filter.)
3. Brakes. weak brakes and heavy vehicle.

The one that concerns me the most is the tranny since it can become expensive rebuilding it over time . from what i have read in teh forum some people has managed to swap a 5 speed tranny, would this eradicate the tranny heat and weak problem? so i dont have to worry about rebuilding int he future? if this is true how much does that conversion cost?!

Please correct me if im wrong and feel free to add any information