Just the replacement mast should be all that's needed (if you can still hear the antenna motor run). I bought one off of Amazon, works fine.
Getting the old one out required a worrisome amount of force, but mine popped out without breaking the plastic "cable". Just unscrew the little bezel, have someone hit the antenna-up button, yank it out, slip bezel onto new mast, then feed the new one in and screw the bezel back on.
As long as the plastic gear didn't break off in the motor, just do like mentioned.... unscrew bezel, pull on antenna while someone hits the up button (make note which way the teeth face Front or back). Generally the same for installation.
Consider spending the extra coin on the OEM mast. Mine was likely an isolated incident, but the cheap mast I purchased off eBay lasted only 12 hours and failed in such an awesome way that I had to pull and disassemble the motor to remove the plastic geared cord which was stuck in the motor.
After that, I bought an OEM mast and it's been fine for 3+ years.