The kit on eBay comes with the code box, barrel and key so it shouldn't need programming which can cost more than the kit they are offering anyway.
The earlier style ECU could be "virginised" basically setting it back to factory ready to pair with the code box in the car, once plugged in it codes itself to the existing immobiliser code box, I don't know if the micro ECU can.
You don't necessarily need to use the barrel and key you can just change the transponder chip into your old key or you can have a second key cut off your original and clone the transponder from the donor key to that.
Changing the barrel is easy though, remove any cowling, turn your key to the first notch (mar?) Then there will be a hole that you can push locking latch through allowing the barrel to slide out.
If you suspect the fan is faulty it could have a short on the fan itself or the relay or high resistance in the plugs causing high current draw, check your fuses and relays before assuming the ECU is toast.
It's highly likely that you could have just blown some fuses.
Iirc the MPI cars have an ECU controlled fan relay, with a main 30a fuse for the fan and a 7.5a fuse for the relay. Disconnecting the temperature sensor should kick the ECU into failsafe mode and put the fan on.
Disconnect the fan and see if the car will fire up?
If it does it may be possible to retrofit them older style fan switch into the radiator to bypass the ECU fan control.