Thats how I did mine as well. Had a half cut from a 4 door integra DC2, and transplanted the entire wiring harness back to the connector at the rear of the drivers seat (RHD , btw). Took out a lot of wiring - power windows. power and heated seats, auto tranmission, SRS system. About 3.5 kilograms worth. Only made one mistake with the distributor/tacho wire, which needed redoing. I did remove the harness and connector that the diagnostics use, which I kind of regret but with an aftermarket ecu was not a real problem.
I'd suggest using the donor instrument pod as well, to avoid rewiring all that. Bit fiddley to fit into the G3 dash, but less work than rewiring.
Otherwise, if the G3 is already FI, you can just add the necessary wires and the adaptor harness for the ecu. 10- 15 wires sounds about right - extra for the distributor, extra for the electronic idle control, extra for the vtec and knock senor, and a 4 wire O2 sensor.
If you don't already understand car wiring you will be a gun after this swap.