Just had another look at your pics, one half of the hinge is in the fiber glass. You should be able to cut this out using a grinder, make sure you rough up the surface of the old glass with a wire cup brush on a drill this will give the new glass and resin some thing to key into.
As for applying new glass matting it not that hard, mix your resin to the instructions paint the area liberally with the resin, put your new hinge in place (use a few bolts to pull the hinge onto the roof and to get it lined up with the old holes), apply more resin onto the degrease hinge, lay new glass matting over the top and apply more resin with a brush, and work into the matting. A decorators wallpaper edge roller can be used to push the matting down. Use the brush or roller to push out all the air bubbles. If more layers are needed apply more matting and resin.
I would give the whole thing at least a week to cure before refitting.
