I have a 96 Maxima and at one point the car had a Nissan remote for the alarm but it was lost. Is there a way to reprogram a secondhand unit to my vehicle?

 

Yes, there is. And has been posted on here many, many times.

 

-Close and lock all doors
-Put the key in ignition 6-8 times within 15 secs
-When hazard blinkers flash twice (program mode)
-Turn key to ac mode (furthest without starting car)
-Press lock or unlock on remote, you should get response if it worked.

Thats what I remember off the top of my head. Thats pretty much it its simple and only takes secs. Done it to my 4th gen and now my 5th gen.

Good luck