Obviously, if swapping in the other power supply does not cure the problem, then it isn't the power supply that is the problem (if you know what I mean).

As for the PS fix, it is not a difficult business - nothing near as hard as replacing the capacitors on a logic board. All you need is the instructions I listed, the best part of an hour, a power drill with a 1/8" or so metal drill bit, and a soldering iron/flux/solder. Piece of cake. Really.