Wiring harness question

I'm putting a D15B7 from a DX into my 93 CX (D15B8) and have gotten different opinions on the wiring harness. I know that I'll have to change the ECU to a P06, but the shop doing most of the work tells me that the harness will need to be changed as well. I'm a broke grad student and I can't find a significant difference for that to be necessary. Any help is appreciated....my car is dying.