OTR microwave turntable won't rotate

Question

My OTR microwave oven turntable won't rotate. Instead it makes a grinding sound. When it first started to fail, the turntable still rotated intermittently. But now it never turns.

My guess is that a gear has stripped or the coupler between the turntable 3-pointed star and the motor has cracked.

1- How do I take apart the base of the oven enough to get to the turntable innards and check out my theory?
2- Can I order a replacement turntable coupler and replace it myself? I'm a bit handy with small tools but have never taken apart a microwave before.

Thanks!