Trying to determine WHERE to look to get sliding door track assembly replaced.

What is your question?

Door was stuck in open position and in the process of trying to get the door closed so I could bring my family home the rail and panel were damaged (I determined that the pins by the roller were worn down to metal causing it to lurch and stop every time I tried to close it). I need to replace the rail, the pin&roller assembly, and the panel that goes over the rail. Is this a repair to be done by an auto body shop or a mechanic, since it's not related to the functionality of the engine?