08 rear brakes

Had my 2008 forrester inspected today at the dealer and was informed I need to have the rotors cut and new pads installed on the rear. I have 32,000 miles on my car and was surprised to say the least. It's been my experiance that the fronts go first and the rears seem to last much longer. The cost would be $351.00 to have this done.
How difficult of a job is this and when researching the info it was mentioned that a spindle nut must be replaced. What is a spindle nut and where do I buy one (dealer). I have done the rotors and pads on my f150 ford and had no problrms. I assume that it's a easy job on a forrester but you know what happens when you assume! Thanks in advance.

Just did the rear brakes on my 03 forester today yes there is a big spindle nut you must take off in order to pound off your rotor.