Need help...rotor mini...

Hey im new here, and i own a 84 mini couper and i want to stick a 12a NA or single turbo in it....i also want to make it rwd...but i hear u have to cut a whole in the firewall and but the gearbox inside the car.....

I was wondering if anybody would know exactly what i have to do
If any1 knows any1 who has done it b4 and knows how much it costed them...