I bought a 2nd hand Jimmy Lewis Super Frank that turned out to have deck delamination around the vent plug. I routered out the soft deck (and unfortunately the vent plug too), filled the hole with 2 part expanding foam and glassed over. Board is now ready to surf again.
Do I need to reinstall a new vent? I intend to take the board on a plane at some point in the future.

And if I need to reinstall a vent plug, is the installation process as simple as
1) router out space to drop in vent plug
2) mix thick batch of q-cell resin
3) pour q-cell mix into hole
4) squish in vent plug
5) when q-cell mix dry, sand off any excess and then glass over vent plug (is 2 layers of 4 oz cloth enough)
6) when dry, sand, paint and go surfing?

What kind of vent plug windsurf type or goretex. Just make sure it is vented to the core, me I would go windsurf type less $$ you will always know if it working.

Original was a goretex vent. I would replace with a cheap windsurf vent.

I would too

be aware that you need the newer style chinook insert as the old one is not deep enough and the cell mix under it obstructs the screw from going all the way in
look for the one that has the bottom plugged with foam that looks like a packing peanut then it's easy

This is what chinook had on their website:

chinooksailing.com/products/1-board-vent-w-slot


It arrived last night and I glassed it in this evening.

what did the bottom look like..... just flat?

The bottom was open. If necessary I will use a screwdriver to make sure open to foam.

Beginner error, looks like resin dripped down sides of screw and now it's glued in solid. Trying to unscrew it is just damaging the head (softish plastic). Smack my head. I screwed up. Do I router out entire thing and start again, or is there some way to save it?

Chinook used to make a vent like this for retrofit