I just took 4 of them out on my H30. Yes, take the screws out from the inside flange. It won't move since there is tons of caulk still holding it in. There should be a trim ring on the outside too. Some people just attach the outside trim ring with caulk and not screw it down too. Anyway, remove the outside trim ring. Gently pry the inside flange up to break the caulk seal (they may have used butyl tape too). From the outside, dig out all the old caulk you can. You should be able to just push the whole portlight through once the caulk breaks free.
p.s. Be very careful prying on the plastic trim ring and flange. Mine where the originals from 1979 and busted into tiny pieces. Probably best to run a thin sharp knife under it first to break the caulk seal. I was replacing mine anyway so I didn't care. Also, do a search on Youtube on portlight rebedding. I found a few good videos of the procedure.
