Hey Claire
What a bummer.
Some years ago when I was running a resort in the Lembeh Straits, I needed to replace the front glass of a macro port. Luckily for me, one of the wizard techs from Reef Photo was staying at the resort and with a couple of very simple tools, he removed and replaced the glass inside 10 minutes. (I had bought a spare).
It wasn't a complex task - installing an o-ring and then prising the lens into place. We had not means for pressure testing it but certainly did the first dive with no camera in the housing.
Maybe an outside thought, but it could be worth flipping an email to Reef Photo - who are really helpful - and asking if they can give you a bit of guidance?
Good luck with it. I really hope you can get it sorted.