Anyone know how to remove the factory antenna on an 88 cavalier?

Remove the mast, then unscrew the flat nut that has the 4 little slots in it.

Damn years ago I had a how to with pics and everything...

Remove the antenna plug from the back of your radio or aftermarket set
Remove the front headlights on the right side of the car (might have to do the whole set, cant remember)
Remove the wheel well trim screws that go around the fender
Remove the 2 large bolts holding the fender to the frame under the car, and keep track of those shims that fall out
Unscrew the antenna mast from the mount
Pry off the little cap with a flathead screwdriver (counter clockwise!)
Remove the line of 13mm bolts that hold the fender to the frame in the engine bay
Remove the two 13mm bolts holding the antenna base to the fender
The fender will come free at this point. Pull out the antenna base. Set it aside
Slowly pull on the antenna cable and it will feed through the rubber grommet in the firewall

You will need to patch the hole in the fender.
I chose to replace the antenna with a very small profile one that I mounted to the top of the windshield in front of the rearview mirror, and ran the wiring under the headliner and down the driver side A-post and across the bottom of the dashboard into my CD player.

This was done on my 89 Sunbird.

Before:


After: