Clutch replaced, but still will not shift???

I have an 03 X-type 3.5 manual trans. My clutch went out recently and I had it replaced, but after everything was put back the car still does not move. Sounds like a grinding noise when you try to put it in gear and go.  Mechanic told me that most likely it is the flywheel??? Just wondering if anybody else has had this problem or any idea what the solution is. Thanks