hmmmm does the Pulsar go by any other name/model? b/c i was looking on the12volt.com and they don't even have a Pulsar or NX listed...
i know some imports ground through the chassis, meaning that u have to screw the radio in for it to work. is the antenna power? I really doubt that the stereo and dash are going to ground through the antenna. actually the power antenna wire is a +12v so it wouldn't be ground. there must be a loose/wrong connection in the wire harness or something

i just checked and the harness is the NWH-700, that works for all Nissans up until '95 so maybe u might wanna try getting a new harness and see if that works *shrugs* wait....is there even a stock harness in there? or are the wires all cut?
other than that, check ur fuses. u may have blown the fuse to the dash lights while working on the stereo...it happens.....