I've had to change the pump head o-ring, and it can be done on the car.
I also changed an input seal on the motor, and it was super easy not in the car. I think you could do it at least on a 700 by jacking up the back of the tranny, but it might not be worth the sturggle vs removing and retiming the pump.
For the pump head, read this thread, and understand it fully before you begin.
http://www.vwdieselparts.com/forum/v...ce6ed&start=15