I was wary of the electrics too mate when I did a very similar conversion but found it actually very straightforward, i took the loom from the donor car and laid it down, worked out what everything was and just carefully put it into the other car, it just falls into place and a lot of it is colour coded. Would be handy if your mate or summat had another RST you could use for reference though.

I reckon the cost of a garage etc to do it would be quite expensive but i could be wrong

Good luck anyway