Hi Oliver,

To replace the lens you need to split the two halves of the frame of the moving part. These are basically two C-shapes that are mirrored relative to each other. The eindpoints are connected with small screws and a connection part that slides in the frame. The split is across the length axis of the boat with one split between the hinges. To take it apart you must separate the moving part from the part screwed to the deck. Getting the screws out is a pain and is better to be done in a workshop.
But first you need to get the hinge-pins out, that can be a big problem as well. On our 54 they used a trick to break the hinge-pins to free the moving part. In the workshop they removed the remains and replace the rubbers. Back on the boat they used new pins and adequate quantities of anti-seize paste (Duralac/Tefgel).
I agree with a previous contributor that it may be cheaper to buy new hatches. The problem I saw was that Amel used a high-gloss frame and all the ones I saw had a matte frame.

Regards,
Arno Luijten
SV Luna,
A54-121