1997 Range Rover New Front Differential, but fear default s

Shakes or Wobbles problem
1997 Range Rover V8 Four Wheel Drive Automatic 148k miles

I recently had a new front differential installed and went to pick it up at the shop and it was pretty shaky and the gear default light was still on- along with the fact that it is definately not changing gears smoothly. THe car is also idoling high, so from park to Drive it goes by itself. It seems to idol higher in park- which is wierd.