I am trying to remove the seat belt retractor (seat belt unit) from the back of the seat of my 05 Yukon and don't have a clue how to get to it. I can see the seat back cover has to be removed and can tell it is attached at the base of the back. I can't figure out how to remove the arm rest to remove the seat cover. Is there a way to get to the seat belt retractor without completely removing the cover? Why I need to do this I have described below, which may or may not be important.

I bought my SUV from a salvage yard and rebuilt it. It is complete with the exception of resolving the issue with the SDM and seat belts. The driver and passenger airbags both deployed. I replaced both airbags, tested the sensors on the front, and had the SDM reprogramed. However, when I installed the SDM the light on the dash did not go out. I had the truck scanned for codes but the scanner couldn't communicate with the SDM, like it isn't programed. I am told it is because the seat belt pretentioners must also be replaced, which I am ready to do, but don't know how to get to them.

Any help is appreciated.
Craig