Living up North and working on cars SUCKS! I absolutely hate rust. So yes, they can be a pain to work with, but alittle (or a lot) PB Blaster (penetrating oil) will usually work.
For $700 you can search the "rotor over hub" swap and do that for less. I'm curious as to why they want to charge you $700 even if the bearings are stuck to the rotors, especially since you brought them the rotors.
Sorry I can't give any tips on removing them, I just got this car.