If the licence fee has already been paid you won't have to pay that again. Any ECUtek mapper will be able to map it but they will start from scratch, so even without the licence fee it will be around £350 I believe.
There won't be any way to tell if it's genuine without getting an ECUtek mapper to look at it. There are no physical changes to the hardware, only the ROM/map is encrypted.
You will need to have the keys re-coded to the new ECU/immobiliser or it won't start. Or did you get the existing keys/PIN code with the new ECU?
As above, Bob and Andy are supposed to be two of the best mappers in the UK, although I'm only going off other people's advice on that.