Advice A : take it to a surfboard repair shop
Advice B : Refer to advice A
You got the damage over a month ago, and now wasted another week. Get it to a repair shop and get it done right.
BUT..... since you probably won't....... the video OMS posted is a " full on " repair where both plugs rip out with some foam removed. The guy has the FCS install kit, most shop don't have those in stock and need to order it.
Your damage is a much simpler " push down ". Glass is mainly intact and foam has been compressed.
1)If the plug isn't damaged, pull it out, clean it up.
2)Lightly sand down the glass around the hole. 3) Tape the whole area ( like a foot around ) and cut a ring a little bigger than the hole.
4) screw the plug into the tab of a fin but let it float up a bit so it doesn't contact the resin. ( you should shim the other plug so the fin is level. )
5) cut up some fiberglass cloth like beard shavings
6) mix that into resin
7) add the proper amount ( let it go off slow not fast ). Weather and time of day effects that too.

Put the resin in the hole and push the plug down. Resin is going to flow out, so tape up a lot.
9) before the resin gets too hard, cut away the excess around the hole. ( how do you know when it's the right time ? Experience. )
10) pull off the tape and sand down with a wood block.
there are too many variables to go wrong. Yes, I agree " there's a first time for everything ". But bad things happen when you're in a rush and ill-prepared. I do repairs and have tried to talk many customers ( especially broke college kids ) from doing it them selves. Most come back with a much bigger problem, time and money wasted. Hindsight is 20/20. I wish you luck on your repair ......( err, I mean your dad. )