Contact a company called 'BBA -Reman' they are very good at what they do and will be able to look at your current ECU and make a decision whether it can be repaired or not, they should be able to supply a new one if its not repairable and should be much cheaper than the dealers
highly doubt it, probably just the 25amp fuse to the starter has gone
the ecu is waterproof, you could leave it in the bath overnight and it would still work