ALSO - quick question... On the combat tables and repeating 20's. I used THAC0 more than I ever used these tables, and they are messing with my brain. Say I'm a 1st-level fighter. I have a +2 to-hit from strength. If I am unfortunate enough to be attacking a foe with a -5 AC, do I need to roll an 18 to-hit, just like if my foe had a 0 AC?
Could be either, actually. See top of DMG p. 82. There's an option there to either (a) treat it like any other number, or (b) treat the second "20" as meaning "natural 20 only".
When dealing with THACO/attack bonuses, I treat a natural 20 as "25", which is more like option (a) but synchs up with the 21+ numbers that come later.