Well, it would be really helpful to see how the motor is situated, but in the absence of being able to do that I am thinking that either

1. you did not get the motor on correctly

or

2. you did not get the wiring connection back onto the motor correctly

or

3. something else has jammed the motor

and it is drawing too much current.

I think you are going to have to take the new motor back off and inspect the transmission, making sure it turns. If it does then see if the motor turns freely and replace it, along with a new wiring harness.

Good luck