This covers the simple installation procedure ... many get away with this.
However there are times when it can be more difficult, telephone and I'll run over it.
However if I am not around the following may help.
The antenna mast has a metal sheath wrapped around the mast. The old sheath can get trapped by dirt over the years. There is nothing but dirt holding it in - no screws, clips or washers. Lubricate over a period of time to dissipate the dirt. I have had to stand on a chair to get full leverage at pulling a mast out before now LOL.
If the mast pulls out and leaves the sheath in place then more lubrication, I have found that a pair of long nose pliers inserted (closed) and then opened and twisted can help.
Finally the plastic cord can be broken inside the motor and may require removal of the motor and slight disassembly to remove.