Careful work (and many $$) pay off. I replaced the system board AND power supply following the instructions on the Dell website. They are actually pretty good. But not nearly detailed enough. Plus there are many wrinkles that you can run into. Replacing the Dell system board is not for the faint of heart.
Given an hour for a Dell web wizard diagnosis (that may or may not be correct, it was not specific as to which FRU needed replaced), 2 hours for an erroneous chat diagnosis, and 2 hours for a final diagnosis, 48 hours for next day air, 3 hours for replacing the system board and power supply, an hour for Ubuntu memory testing (probably not required but the memory (not all Dell) was suspect before) and filesystem checking, and another half-hour for getting Windows 2000 to plug-and-play, it might be a good reason to buy the extended support.