The rear is relatively easy.  Relative to the front.  The covers are a bit
of a trick to get off, other than that it is painless, other than to your
knuckles.  The front blows.  If you every have to do anything to your front
heater core, replace the core and the blower.  You don't want to do it
twice.  You will understand the first time you do it!!!!!

John
87 Westy SVX
91 GL 2.5 Subie (front heater core done by Vanagain - thanks)