You did OK. Your Local Dealer would not impress me charging $75 for the Transfer Fee. Did he make you hold your hands in the air while processing your transaction like Jessy James? My local dealer charges $20 which might be a hair low, but $75 is robbery.
You will like it. It will need a little TLC to be Perfect. If you are planning on a long time relationship with the old girl you might want to down load The Ruger SP101 Trigger Job Guide by Kevin Wilson. I know you have a GP100, but both have the same basic parts design. The SP101 info was better than what I found for the GP100 Trigger Job.
TriggerShims.Com sells both the Shims and the Wolff Spring Kit. I use the .005 Hammer Dog Shims, .005 Hammer Shims, and the .003 Trigger Shims. You will get 3 Hammer Springs in the kit and 2 Trigger Return/Latch Springs to experiment with.
Follow all the instructions and you will be fine. Watch a few You Tube Vidios to get up to speed on how things come apart and go back to gether.
If you want more details e-mail me direct.
Bob The Revolver Guy