I keep hearing about Edwina, and I'm under the impression that it's Edwin with a sex change, but could someone enlighten me as to what happens...since I'm about to take him into my aprty for the first time in BGII.

It's linked to his quest in the cemetarry, where he wants to find the Nether Scrolls. Once you have them, let Edwin keep them. After some banter conversations Edwin will try to use the scrolls and be transformed in Edwina. There is more to this subquest after he gets transformed but I can't give any further details since I never did that part.

Edwin reads the scrolls thinking it will transform him into a lich and it backfires, of course. The subquest continues and Edwina will eventually turn back into Edwin, but I don't want to spoil further unless you request it. Except for getting the Nether Scroll in the first place, it all works itself out with little intervention from the PC.

I would recommend getting the scrolls ASAP as they do provide Edwin with some beneficial bonuses as well.

Important to note that once you get the Nether Scroll you're given 2 responses to Edwin. Only the "Will you be using that scroll to help us?" option willl continue this storyline as this option sets a Local Variable and the other a Global Variable.

Its really quite a funny quest, the Blackisle team actually recorded extra speech for Edwin as a female, you'll hear him say the same old things Eg. "What is it now?" & "Go bother someone else" but in female speech. Plus after the quest he gains a few more abilities and something like +50 lore. Can't beleive so many people have played without EDWIN before! EDWIN!

It's a shame that you can't keep Edwina. Her dialogues and party interactions are hysterical -- far funnier, I think, than Edwin's.

What I didn't realize, however, was that she got extra abilities. What does she get? Is this while she's still Edwina or after she reverts back to Edwin?

"She" gets a lore bonus and 50,000 EXP.

I don't recall there being any other bonuses, though I might be wrong(I haven't played the game in over a year).

IIRC Edwin also gets a permanent +1 bonus to saves from the scrolls before transforming.