I am currently eyeballing a 96 A4 quattro 2.8 V6 auto. The transmission is said to be 'slipping'.

I am not so familiar with auto trans, but what makes a trans 'slip'?
I would need to drive the car 50 miles. Would that do further damage?
The plan is to fix the trans, or find a used one and change out.
The recent clutch changes on my 98 manual indicate that changing the trans might not be too difficult. Or is it?

 

A bad torque converter. Basically its causing the stall speed to get higher in the rpms.