Slipping clutch? Help Please

[91ma70]

Sorry im new to the forums so excuse me; i just bought a 91 NA Supra which has 187.5k on it and the clutch is slipping in first. I am going to replace it and the mechanic is going to charge as much as $850 for the(clutch disc, throwout bearing, pilot bearing, pressure plate, resurface the flywheel, replace tranny mount, replace fluids and the rear main seal which is leaking) including labor. Im guessing that it was oil contamination from the rear main that caused the slipping. Do you guys think that this is a good price? Also, another question- when driving in 5th gear the rpm are over 3k @70mph-is this normal? I'm used it being under around 3k in other cars. Anyway i still love this car!