Wiring on a stock nissan altima stereo

Ah I was gonna type all this out from memory but then I remembered they have nice lil pictures to go along with it, so check this out instead:

http://carstereohelp.com/stereoremovalNisAlt.htm

sorry i kinda didn't give you much info as far as the RE-installation is concerned.

You'll need the two metal radio brackets that hold the factory radio in place.  Almost always they will be attached to the aftermarket unit that is being removed, so just remove the two screws on each side of the aftermarket unit and the thing will pop right out.  If this is the double-din sized factory unit then there will be four screws per side, and just put the bracket with the "r" on it on the right side and move it around and it'll fit in one spot just perfectly.  Same thing for the left side.  then screw in the bracket to the unit, remove/unplug any antenna adapters that may have been used with the aftermarket head unit, and plug in the antenna cable.

Was a wiring harness such as the Metra 70-1763 used to hook up the aftermarket head unit?  If so, just unplug it from the factory wiring and the factory plugs go right into the back of the factory unit.

If a harness was NOT used, you'll cut off the aftermarket harness (make sure you leave as much slack in the factory wiring as possible).  Then you'll need to grab a Nissan reverse harness (Metra 71-1763 or equivalent) and, using this wire diagram and a multimeter to verify the wires, you'll hook up the bare wire ends of the reverse harness to the bare wire ends of the vehicle's wiring.  After you solder/crimp and tape all the connections up, just insert the plugs into the back of your factory radio, secure it with the 4 screws, and then reverse the dash removal instructions that you used before.