Doug,
I can explain the step by step method to get your HH out of the cabinet. Basically, disconnect all the wires, drain coolant, hoses and disconnect exhaust connection. The basement door will need to come off. The frame around the opening will come off. The HH has a couple of screws in the bottom front flange that will need to come out. Then just slide out the HH unit.
Good luck, call me if you need help.