Gilling a fish is quite safe providing you don't put your fingers in too deep. If you just follow the gill cover your fingers will stay clear of those 700 teeth!
here is a picture that might help, not a bg fish, but ti shows how you stay clear of trouble.
Funny, I have never had a pike take a fly deep, they are always hooked in the jaw or close by.

The fly is quite clearly visible in the jaw.
and again here:
If you are fly fishing for pike it is worth joining the Pike Fly Fishing Association. It is only £10 a year. You'll get that back in fishing invites to private waters that you cannot buy fishing on.