The old glassed over hatch
ploy, eh? That leaves you with one of two choices; 1. Unglass it, 2. Make a new hatch.
Is it a thin layer of resin over the hatch? Can you see the screws? If so tapping around the old hatch with a chisel shuld break it loose, then use a hammer to tap in a screwdriver into screw heads should break through enough to unscrew. Mine wasn't glassed, just painted, and I had to do the same thing.
If it is more severe than that there may ba a hatch underneath, or from the engine
room, (it may be behind insulation
, or foil/foam).
If you can post pictures of as many sides directions, as you can.