More than likely it's just dead. If the ECU isn't communicating with anything, it's pretty useless. Not knowing exactly what he did (what parts he replaced inside of the ECU) and not knowing the damage to the ECU in the first place, it's pretty hard to tell over the internet. It sounds as though your auto electrician was trying to save you some money by trying to fix what was wrong with the ECU, so don't kick him for that. If the mechanic says it's dead, it's more than likely dead.
As an alternative to a "new" ECU, you could possibly get a used one from a junkyard or off of eBay. A used one may need to be programmed, but it should save you a ton of money over doing something like ordering a new one directly from Opel.