You can test the motor before having to replace that.
What I did with the slide motor was to get at the two wires it has close to the motor, cutting the insulation on both. Then I used a portable charger with clamps and found that it turned one way and then the other way with the clamps reversed. So the motor was ok.
That left a wiring issue which turned out to be the switch in my case. It was tricky wiring the switch so it would work right.
The link above has links to trouble shooting videos for the jacks.
