Mike4puy

Need help with this one. I purchased my 2005 Prius just over a month ago pleased thus far but now I have a question for the experts.
The antenna did not have the original mast and I noticed that some threads were showing above the base. I tried to get it to screw in more but it turned but never tightened up or came out for that matter. My question and only solution would be to replace the base of the antenna, very costly to have it done and I don’t want to attempt taking out the head lining, then I saw the Shark fin antenna and figured out that it maybe the answer. Now I need to remove the existing mast from the base that will mean cutting it to find out why it will not come out, then I would hard wire the Shark fin directly to what ever is inside the base unit. So I guess I would like to know just what is under the original antenna base casing once I cut it open because once it’s cut this has to work or I will be without an antenna.
Thanks, Newbie for any help.