If the liner is rotten as you say, it is not a clorox job.
Taking out the liner is a real pita. Just trying to remove the screws without damaging the teak
moldings is a time consuming and sometimes frustrating job, specially on the sides of the cabin where ports leaks
rottened the liner. Of course you have to remove all the fittings and reseal them, which include the ports
on the sides. You must remove all the teak
from the side panels
as well, at least the top bar if you are doing only the ceiling. If you do the sides you also will have to take into account the space the thick panel takes and plan accordingly.
At the end I did the cabin ceiling and one side of the cabin, I used a kind of formica that was not the right one (supposedly waterproof but I can see watermarks). It looks much better than without liners but I will redo it in the future. The v berth is still unfinished. I did spend a lot of time cruising though, so it is a matter of priorities in my case. I did use some insulation
but is hard to tell if it made any difference.
Exmaggiedrum advice sounds good to me and I would probably go that way next time.
Having said all that, I am very happy with the boat. It is a very solid, well built sailboat and a pleasure to sail. I did not find any problems in my mast
step, I think I have a pic of it somewhere I'll try to find it. I'm in the DR but living a few hours away from the boat now so not easy to get new pics.