I reckon you'll be ok with the wiring. I haven't attempted installing a whole loom but I got to grips with some shocking wiring on my series 3 and from a starting point of no electrical or wiring experience whatsoever managed to sort out and fix , no tail lights / no front r/h indicator / no horn / no reverse lights / intermittent wipers and screen washer. All now OK. For me , it all started to click when I realised the wiring diagram is schematic and got the wiring colour codes right in my head so I suspected anything that looked like old mains wire. I also stuck a single terminal block on each wire that ended at nothing.
I fear the engine and the gearbox.
cheers,
D
