Antenna is easy. I chopped mine by a foot with little effect on reception. I lost one radio station that had sketchy reception, but gained it back with a new head unit.
All I did was take a multi-tool, chop the mast with the wirecutter, pull the old tip off with the pliers, put some super glue in the old cap, then slid it back onto the shortened mast. Is is the best method? Probably not. Did it work, and was it free? yes.
Welcome fo FF and good luck with your car! Have fun with it!
ROTM June '13, PNW Crew #42, SR #245, Rally Rev #02