Get a schematic before you do anything! Does it have Vregs on the manin board or just in the PSU? It would be almost impossible to repair the switching PSU, they're a _*****_ to track down when they're not working!
I find it amazing that stuff as complex as switch PSUs (which have custom ICs, HF switching transistors, lowimpedance electrolytics, custom trannie, extensive filtering blah blah) are cheaper than an off-the-shelf trannie and a pair of 7815/7915+7815 :shock: :? :roll: