The controller easily pulls straight out once you push down on two catches which engage its bottom side. But you have to remove the radio to access the catches. Diagnostics for the controller are explained here: http://www.peachparts.com/shopforum/showthread.php?threadid=86546

The expansion valve is in the engine compartment on the firewall close to the brake booster. You will need to remove many of the components in front of the windshield to access it.