Yes, I agree the estimate is excessive.
At $100/ hr for labor, that's 11 hours of work. I would estimate that a knowledgable professional mechanic can install the base plate and the wiring within 4 to 5 hours at most.
I did my 02' CR-V base plate in about 3 to 4 hours and the wiring in about 2 to 3 hours. But, I'm no mechanic and I'm admittedly slow when working on vehicles.
I would shop around for a better deal, even if you have to travel a bit. I would think that around $600 total is a more fair rate.
PS- don't rule out installation by a trustworthy local auto repair shop. They can do as good or better than an RV dealership. Just provide the instructions.