This can be done from the outside. No need for a port. It's not a structural part of the boat, but it needs to be tough to withstand modest impacts.
You'll need to remove all the damaged glass and feather back the edges. It will look much, much worse before it gets better. Disc sander on an angle grinder will make very quick work of this.
You'll need to fabricate a backing sheet of polyester resin / glass to go in the hole and be glued in place with epoxy. Spread out a plastic drop cloth on a firm, flat surface and wet out two layers of fiberglass matting in a rough circular pattern, big enough to overlap the hole by 3" on all sides. After the resin starts to go off, but before it's really hard, peel it up and form it into the rough shape of the hole by inserting it and pulling it back against the sides with fishing line stitched through the apex of the curve. (See "Blind Hole Repair", Hobie HOTLINE magazine here: http://2010.archive.hobiecat.com/hobieclass/eHCA_Hotline05-06_2008.pdf
. Let the resin cure completely, remove and glue back in with thickened epoxy resin (peanut butter consistency and don't be shy about using lots to glue it in).
Once that's in place (plugging up the hole and forming a rough outline of the shape to be restored), start laying glass and polyester resin until the shape is built up. Sand to shape, fair with thickened (Cab-o-sil) poly resin and sand to final shape. Spray with gel, sand and polish.
This can be done in 3 days, most of which is waiting for resin to go off. The only real hard part is matching the color. Good luck with that.