Hi Paul!
It is a nice coincidence, I wouldn't dare to be a pioneer with my Maxi :)
I bought the boat in October 2022, replaced some small parts, rebuilt the whole electrical system (it hasn't burnt down yet knock-knock), changed some lines; I tore the very old mainsail so had to order a new in the autumn. My rollerfurler genoa is in pretty bad shape too, it should be replaced too, but I wait and see, even if I can't convert the boat this winter, it should last one last season and I convert the boat after season.
This winter I gutted out the whole cabin just like you, I haven't removed the toilet yet, but I plan to anyway with or without conversion. I scraped off the white-grey linig, it was covered with mold in all the hidden inner curves where it didn't stick to the GRP. Best way I found to remove the lining was a putty knife with it's corners slightly rounded so it didn't tear that badly the lining.
Removing the glue is easiest (for me) with isopropyl-alcohol brushed over a small area (like two palms) then wire brushing with an accu drill with an ca. 25 mm diameter brush. Larger diameter brushes bit into the GRP, the small one doesn't. I shouldn's say, but wear a proper mask.
Scraping the lining took maybe 3-4 days, cleaning the glue is taking even more, it's not yet finished. It got cold here too, maybe I ice the project until March.
I'm rebuilding the two closets too, in an open interior style, up to the inner shell only. Probably I spare the kitchen, it's in better shape, I only change some doors probably.