Just buy the part for 5$ and replace it yourself. If it's the part that I'm thinking about, the one that moves up and down along the pillar trim and holds the belt, you can just pull the pillar trim out (it's held by clips) and pop the new one in. 10 second job.
Or just have the shop do it and tell them you refuse to pay 75$ for them to do it. The guide is plastic, it's not going to desintegrate due to sunlight. All my trim and plastic is original, and for the past 10 years, all owners of the car have kept it outside.