I have both BG I and II, followed the various setup guides, and am about to start BG II. In the process of figuring out importing my BG I characters and making my party, I was reading the gamefaq's entry on BG II:

http://www.gamefaqs.com/pc/258273-baldurs-gate-ii-shadows-of-amn/faqs/34147

In there, it mentions there are two bonus CDs that folks could get for pre-order or collectors edition .. Those CDs add some extra shops that have cross over things from Planescape and Icewind Dale.

It's not clear if the GOG version of BG includes that material or not (or how I can verify). The FAQ does say how to use cheats to create the stores, but I'd rather not do that, yet ..

One of the bonus merchants can be found in the adventurers mart in Athkatla and is already in the game. The other is added with the Baldur's Gate II Fixpack.

Don't forget to read the mod guide stickies!

Ah, I will go back to read them closer -- I followed more in the mindless "install x, y, z" steps, and did not look closely at what particulars were installed with them.. I'll go back and check now. Thanks!