subaru brakes are easy to change. If you have any mechanicing ability, you can do the brakes. I don't think you'll have to worry about the caliper needing to be screwed in. I haven't run across that on the newer subarus.
re changing the pads & rotors, if the rotors aren't giving you shudder or don't have huge grooves, they're probably fine. You may want to sand them down to remove any old pad material.