Well, if they calculate 1 to 1.5 hours of shop time per U-joint, you are up to your $300 quote right there. They shouldn't be all that bad to do. You should be able to knock them out on a weekend. I'm sure if you ask for advice you'll get a bunch of walk throughs on how to do it.

 

personally if nothing goes wrong i can do a u-joint in about 30-45 min but ive done a lot of them and most shops do have min times