$100 is very reasonable if you know the shop is reputable and guarantees their work.
Occassionally, while installing a radio system, for say a police department, the equipment fails to work even though I've wired everything correctly.
I have to figure out the faulty equipment, remove it (after I've already installed it) and arrange a replacement with the factory.
Then, reinstall and test again.
I still have to make it work cause that's what the customer pays for.
By the time I've gone through all that it's like doing 3 installations, timewise, and if there's another problem during the warranty period I have to return and fix it again.
Anyways, if the shop is legit, you pay $100 and get a fully functional guitar as asked regardless of what they had to do to accomplish that.
If you think you can do it and save money then take the time (as in time=$) to do it yourself and hope it works right the first time.