while I don't have any special expertise at this, I'm figuring that a multimeter will go a long way. Signal and/or power is not getting to the flash and I have to figure out where the problem is. I don't know what is supposed to be connected electrically to what, however, so I can't check it.
I know it 'should' go to canon, but Canon is going to charge an arm and a leg, I'm pretty sure to fix it, I'd guess. I suppose its worth checking out. As 10D's go down in price (watch the ebay prices drop when the rebel replacement hits the shelves!) it makes less sense to spend lots on a repair. It all depends on how much.
If I could fix it myself by messing around it'd be fun. Besides, then I'll know a little something when my next DSLR bites the dust in some remote spot. Before I was afraid to take it apart even. Now, that's the first thing I'd do if it got wet again.