It's been a few years since I did this, but as I recall removing and re-installing the hatch is pretty easy. In my case it was done to rotate the aft hatch so I could install a rigid boom vang.
First remove all the screws on the plastic trim, and remove the trim. When you do this, you will see how the hatch is attached. As I recall it is bolted - screws into the core are not a good idea! And Pearson makes quality boats...
The hatch/deck seal used the dreaded silicon caulking. I removed this (scraping, and eventually sanding) and then used butyl tape to bed it down. Removing the old caulking took more time than anything else.
I do not recall any voids needing filling/sealing - so nothing like the ports. Personally I would not want to permanently epoxy the head liners in place, as I may want to remove them at some stage for adding new hardware.
So I know, a bit light on details, but the removal was very quick, easy and intuitive!
I also replaced the round foam gasket. Can be done with the hatches in situ. Cost me $82 in 2012. Double sided tape to hold it in place, superglue to seal the cut ends together. Much better seal than the old dry, cracked ones. A friend suggested wiping all gaskets with Vaseline every 6 months or so, to ensure a good seal, and prevent them from drying out. Don't know if that is a good idea or not..he has some odd ideas sometimes...
I think I got the foam from Pompanette/Bomar, but they seem to be dropping old Bomar products as the Bomar website (pompanette.com/bomar) now no longer exists.
I hope this helps.