Yes, I did. The mast actually stuck due to nylon mast is broken.
And eventually this morning I successfully replaced new antenna. Exactly as you said, after open the inner fender, I saw to bolt and one harness. After removed them, I was able to take the whole thing out. I open the motor by removing the nut. Then I could have a close look. It is the grounding sleeve stuck inside due to some broken metal pieces. I managed to pull the mast out with needle nose pliers. Then, clean the motor, put some general grease in, plug the harness to the motor, turned on radio, feed new mast into motor. Install motor with mast back to pathy.
enjoy...
By the way, the $18 ebay OEM antenna is a kind of longer than original one.