You will probably have a lot of work to make it paintable. I don’t have a McGregor (I assume that is your boat).
If your fiberglass cabin top is anything like mine, it is really unfinished under the headliner...
Around 8:10 on the video, you can see where I opened up the liner to get to the backing plate under a rope clutch.
That would take a whole lot of prep work to get it paintable.
In my old boat (1996 Hunter 280), the fiberglass was pretty rough under the liner was well.
Might be easier to replace the headliner.
Have you opened up any sections to see what you are dealing with ?
Greg