Solid airbag light, no power to stereo? help please

[helio300zx]

Hello all!
recently I decided to change my headunit in my 300zx, to change from a single to a double din, however when I removed the dash and remove the headunit I realized my double din doesnt have the correct harness so I re-install my old single unit and bring it to a shop to install it, however I realized my car airbag light is on, and my amp, and stereo doesnt power on. So I check online and found this helpful guide however his car is the 1992 300zx and mine is the 1991

http://www.twinturbo.info/63104/107976.html

where as mine Look like this. http://flic.kr/p/itDQwS

any solution to fixing the problem of getting rid of the airbag lights + get power to my radio because my car is super load and the music really really helps.

[helio300zx]

and if someone got other ideas for this solution feel free to post it. there is no power for my interior except dashboard, so at this point anything helps, note "its not Flashing" so the door flashing trick doesnt work. I also read I can erase the code with obd1? or is it another specific tools since the 300zx ultimate guide suggest a consult device with Blavzt cable?? and do regular shops carry obd1 or must I drop the car at a dealership??

thank you!