I didn't have any issues reaching the 13mm nut on the top of the mount. Its acually eaiser to reach than the top exhaust manifold flange nuts on the v6 passats. I have stub metric wrenches these work perfect on...purchased a cheap 13 dollar ebay set just for the v6 exhaust, ended up working well on the motor mount too.
I finger tighten the motor mounts in the frame then lower the motor onto the top studs. When removing I take the 13mm nuts off the mounts top and bottom before pulling the motor.
I do all this after i attach the shifter linkage. So much more room to do this with the front of the motor raised as high as possible and transmisson hanging low as possible.