I am just finishing my second right now. I assume they are all pretty much the same..maybe not. I removed the hatch and covered with plastic covered OSB board to keep weather out of the opening. Once I got it home, I took a sharp retractable blade(the type you nip the tip off) and cut the old seal away. Just go down as far as you can and slide it across. It should cut easily. Once the inside and outside seal are sliced, the old lens should lift out. Clean out all the old caulk down to the metal. Fairly easy with right tool. I masked all the edges because I knew I was going to be messy. Also, do a dry fit and trim where the caulking will bond with the lens. By trim I mean trace the caulking area with the sharp blade very lightly, just enough to allow you to remove the protective film where caulk will be.
I replaced both of mine with Lexan cause I thought that is what was in there. Wrong! It was acrylic. Lexan cost me more but it is bullet proof. 1/4 inch 2 x 2 pieces cost me $74 delivered for both. You will need a table saw unless your supplier cuts it exact for you. A band saw is useful for the corners. Finish with edge sanding if needed. I used black Life-Seal $20.00. Make sure the new lens is not below the frame or water will pool on it I used a gray Lexan which looks lighter than the original but looks great. I can see outside easily but still have a tint.
Oh, and but sure to center the lens and caulk in stages. . First set the replacement in the frame on a bed of caulk. Once centered, walk away. Then follow up the next day and caulk to finish the inside with a smooth, finishing bead. Walk away. Then the third day flip it over and caulk the top and smooth it. Walk away. Don't forget the tape. Be sure to force as much caulk into the groove to avoid voids...you will have some but who cares.
I would say it took me about 2 hours for each hatch. Depends how picky you are. Total cost 120.00 for both. Plexiglass would have been a lot cheaper and probably just as good
I may have said too much but you get the idea I hope.
GL