potentiometer

Was informed that I need a new 5th bow potentiometer. Mechanic said it's bad, which is why my toneau cover is not operating. Is that a difficult fix? Where is the best place to get one at a reasonable cost? :o

I am looking at getting a 1993 Saab 9000 CSE but according to the check engine code it needs a throttle body potentiometer. I am trying see if I can even find one and how much one would cost. Let me know if you have any idea where I might be able to get a hold of one of these. Thanks!