My advice is also to contact VEX, however, depending on how damaged the components are it may not be possible to replace them in which case the whole board would need to be swapped.
Last year I did help another team do the repair themselves, or rather I put them in touch with a rework house that I had used who charged them a token fee to do it. There are two different types of FET used for the H-bridge, they also vary depending on age of the cortex although they are all more or less compatible. Here is some information I forwarded to another student last year, if you know of someone who works in an electronics related field they may be able to help you, I personally would probably not try and replace them myself, again my advice is to have VEX do the work.
Motor ports 1 & 10 each use two parts to make the H-Bridge. A dual N Channel Mosfet and a Dual P channel Mosfet. One part is on each side of the circuit board, one or both of them (but most likely just one) may be damaged.
The part on the underneath side of the board is an FDS4935BZ. The part on the upper side can be one of two alternatives, cortex version A3 and earlier used an AO4818B, cortex version A4 used an IRF8313, they look pin compatible and performance is almost the same.
Open up your cortex to try and see which parts are damaged, try replacing those, this may or may not work depending how hot they became and if they caused damage to the board.
You can order from digikey, here are links.
Primary side - N Channel Mosfet
Secondary side - P Channel Mosfet