Power Antena Mast

Any tips on replacing my power antena mast in my newly aquired '98 T-5. I bought the new mast, unscrewed the nut on the outside and ran the antena up, thinking it would just come right out. No way, so I sprayed some rust buster on it and tried again, no luck. Is there something inside I have to take apart? I looked, but nothing was obvious. :banghead:

My old '89 wagon took 2 minutes to change (had to lower it in order to clear garage door) so I went thruogh a few!!