I've purchased BG2 Complete from GOG and installed it and am already playing. I became aware that there are patches/bugfixes that might need to be applied. Can someone please tell me where I can locate these, and whether or not it's okay to install them once I've started the game? I'm still in the Dungeon of Irenicus. Thanks!

EDITED TO ADD: Thanks folks! I really appreciate the replies. They told me exactly what I needed to know. Unfortunately I could only mark one as the solution, but all were useful!

You don't really need a fixpack or patch as the game is updated and works very well as it is. One thing I'd prefer is using the widescreen mod, but that's about it really. You don't NEED anything.
http://www.gibberlings3.net/widescreen/

I prefer to have the Fixpack installed, as it fixes a lot of little bugs.

As for the widescreen mod, there are downsides. Once you've got it installed, you can't uninstall it or your savegames won't work anymore. See Hickory's post here.