It all depends on what failed. Unless you are doing solder, work there is no such thing as a "one small part". Someone with no experience in BeCM workings and repair would be replacing the entire power board. However we would still need to know which variation of the BeCM you have to be sure. I still suggest contacting Scotty who can repair what you have or if something is seriously fried he can advise further.
Sounds like it's just a MOSFET that's failed. They are pretty easy to replace, trying to get working ones off a board are a bit of a pain, but removing a dead one to replace it isn't as bad. Definitely fixable.