I have to replace a seat belt

[Titan4]

I have to replace the passenger side front seat belt in my '95 Supercharged Riv. The one that is in there now locks up after about a foot of travel when trying to put it on. No matter how slow you pull it it will engage the lock and will go no further. I have the new seat belt ready to go ($168.00 from Buick). I will have to remove the rear interior side panel and was wondering if anyone had done that before (removed the side panel). It may not be hard to do, but I have not checked it out yet. If anyone can give me any up front advice it would be appreciated. Thanks in advance.