Like most MB engine bolts, the crank bolt uses a strech shank and
has a maximum service measurement. when you are dealing with torques of around 400+NM, I tend to replace these things.
Just like steering wheel bolts, why chance it to save $4?
Make sure your guy uses the correct balancer counter holding tool! If not, and he uses a flywheel lock or ring gear cheater,
you can bend or even break these crankshafts.
It takes the correct tool to hold these when loosening and torquing. PN# 112 589 00 40 00.
The torque is very important also.
step 1 ----- 200nm
step 2 ----- 95 degree angle of rotation.

Motor mounts are self explanitory.
Good luck.
DR.D