Yeah!! So was the knob just stuck? Years of dried oil can do that.
I often have my plans changed by DH, weather, pets, etc. I totally know how you feel.
I've been that excited.
You can totally do this on your own. Believe me. It was one of the first things I learned, and I'm 100% self taught (unless you count the youtube videos, QB threads, and Interwebs research as being non-self taught. I include research in self-learning.)
Don't concentrate so much on which hole you choose. For now, work on deciding how we need to adjust the tension (tighter or looser based on the test) the hole it needs to be in will just naturally fall into place.
Yes, those bobbins have got me curious.