If you buy a front cut, or engine conversion package, which will come with the engine harness and ecu, all the electrics can nearly be done yourself.
I am no auto elec, and I am doing an RB30/25 conversion to my HR30, starting with n/a engines, making them turbo.
I bought an R32 GTSt RB25DET ECU and loom and I will be putting most of it together myself.
What or how do you call an DR30 HEAVY???? What are you comparing it to???? Maybe compared to a Mini, but to another Skyline, it's one of the lightest. DR's max weight 1250Kg, R31's OZZY sedans 1600Kg, HR31 coupes 1350Kg. How you say heavy????