There are beginner's posts for Baldur's Gate on the board already, but the advice there seems to assume some level of familiarity with D&D, saying things like "Well, if you want to be a tank, spec out your DEX, because it buffs your THAC0."

I have no fucking clue what those words are.

I played Boogerman growing up because nothing seemed cooler than a video game called Boogerman and my friends agreed. I'm older now, and I just want to play Baldur's Gate.

I know the Enhanced Edition is coming out, but I have the GoG version sitting on my hard drive, waiting for me to play it RIGHT THE HELL NOW. Is there a guide out there for people who are absolute beginners, going step-by-step through the most basic of concepts? I want to get into these old-ass RPGs, I really do, but they all feel so impenetrable.

Yes. There is, in fact, a great guide on GameFAQs that gives a fairly comprehensive introduction to 2nd Edition Dungeons and Dragons rules.

My basic primer: Having a low THAC0 and Armor Class is good.

Awesome. Thanks so much.