If the 3.0i is like mine, the fill plug currently being discussed is a steel 17mm hex head bolt on the rear end of the left side of the AT (from memory, but I'm pretty sure). So it is not related to the pan bolts or drain plug down there.
That Irwin set from
cn90 would require drilling a hole through the plug, which might get it done. If you've snapped a bolt, and the bolt head is gone, tools like that will get the stump out. But since the hex head is still there right now ...
Before trying that, I would use a set like this (which I have):
https://www.sears.com/craftsman-10-p...p-00952165000P
No need to drill a hole. This set is similar to the set in post #28 by
wpoll, but this one is purposely undersized, with helical cutting edges so it really locks into the bolt you're trying to remove. Damaging and probably destroying it, but gripping really well.
If you do end up snapping the hex head off, then an extractor set like that Irwin set will do it. Careful drilling with a left handed drill bit (also good ones from Irwin) will be a good way to make a hole. And of course, get any chips out of there before putting the pan back on.
And of course, a new fill plug will be good to have.