Look up the power supply on the web, see if you can download a schematic for it. Then troubleshoot just like you would any other electronic device. Be sure its input is correct before going further, if the input is wrong, the output will be wrong. Does it have an internal fuse? Did the transistor become the fuse?
One question: Why did the PS burn out? Whatever caused the last one to burn out may cause the next one to burn out also. Is something shorted? Check your wiring harnesses for rubbing areas.
Changing part of a power supply is likely to be frustrating unless you really understand how the power supply works internally. Usually when things fail more than one component is involved.
If the transistor became the fuse, there is a reason. Transistors only fail for three possible reasons:
1) Mechanical destruction. (Did it get hit? probably not.)
2) It got too hot. (Most likely. are you providing adequate air flow?)
3) Excessive voltage (did lightning strike? Not likely you would not know.)
As to "can you substitute power supplies".. absolutely! Just be sure the capacity is at least as good as what you are replacing. Not all power supplies are created equal.. the key parameters are output voltage and current as you have noted. Dont overlook the quality of regulation and the efficiency ratings. If heat dissipation was the problem, be sure NOT to get a less efficient power supply or it wont last long. Most modern power supplies are about 95% efficient so you are pretty safe there. The old one may not have been that efficient, power supplies have improved a lot since switching regulator technology became common.
If in doubt, just call ShopBot and have them send you a new Power Supply.
Hope that helps-
"The best thing about building something new is either you succeed or learn something. Its a win-win situation."