Good idea on waiting. Ironically, the forward head seat just broke (It never gets used), finding one will likely not happen in the island , saying supplies are limited is an understatement.Maybe hold off on that 'til you're back home with lots of supply backup. Actually, there's really no need to remove other than to look inside and possible cleanup of crud.
IF you get so bored you find yourself just HAVING to remove the plug, try heating the plug and tank, near the plug, with a hair dryer until both are hot to the touch. Attack it gently and it may unscrew a lot easier than when cold.
Good luck .
As for bored, it will never happen
As for heating up, the ole heat gun stays on board, it comes in handy more than I could tell.