Surprisingly wasn't too bad, I literally just had the electric auxiliary fan replaced, hooked everything up again and it ran like a charm. Incredibly the drivebelts and other components weren't damaged by the fire. The only other failure was the battery. Before the fan died and burned it repeatedly kept running after the engine was shut off because the circuit board was malfunctioning (a prelude to the fire which I only later found out) and that drained the battery more than once which ultimately killed it for good.

That said it was the factory batt so it lived for 20 years and 300.000kms which isn't bad. I later read that when this car was still being produced this design error in the fan circuit board which didn't have a cut out that prevents it from catching fire resulted in countless E46s burning out completely after owner's had parked it and left. BMW's comment back in the day was "the auxiliary fan design error can lead to a fatal failure which in the worst case can lead to fire in the engine bay and potentially total damage if the power is not immediately cut from the fan." - yeah thanks for the heads up :).