Here are the parts
Replacement parts for GE GSD550T-60BW | AppliancePartsPros.com

Sounds like a motor problem
Remove the kick plate do not latch the door.
Remove the wires from the motor. Note which goes where.
You should see the cooling fins at the back of the motor.
Try turning these with a small screw driver, if the will not turn your motor is jammed.

Remove the sump cover (inside tub center).
Note how the internal filter goes, put it in wrong when you reassemble the unit and the chopper will eat it.
Check in the sump for debris or something wrapped around the chopper.
Be care often there is glass in the sump.

If you want to see better, remove the water from the sump, a turkey baster works good.
Just remember to add a quart or so of water before restarting the unit.
The seals in the pump will burn up if it is run while dry.