Nah, discussions here are fine, though I'll try to grab you on AIM some time soon just because it can be more convenient.
As for material, probably the most useful one would be the Planar Handbook. The Manual of the Planes is handy too, but a lot of it's been made out of date, since it was a 3.0 book. Unfortunately, these won't have a lot of information on Planescape specifically
, since it was a 2e setting. They'll have bits and pieces brought over from the old stuff (Planar Handbook especially, since it was co-written by one of the major Planescape writers), but mostly generic stuff. If you want info on the setting itself, you're going to have to grab copies of the older books. The major ones there would probably be the Planescape Campaign Set, obviously, and the Planewalker's Handbook. You could also poke around at Planewalker
, it's the unofficial-yet-WotC-approved source for 3.5 Planescape. There's also a 3.5 conversion project that's been going on there. Go ahead and check into that (it'll be linked from the front page), but ignore most of the setting background. It's not out of date or anything; just the opposite, since it's set past the "end" of the metaplot from the official stuff, and we're still set some time before that. Most of the rules stuff is fine, though
Oh, one note: we're not using 3.5 exactly in the game, but instead the Pathfinder
system. It's a long story why it exists, but basically it's a continuation of 3.5 being published by Paizo in lieu of converting to 4e. However, it's pretty close to standard 3.5, and purposefully - it's designed to be compatible with all already-published Wizards products - so no big worries there. It's also in an open beta until August '09, and so it's free to download, though you do have to register to do so.
Also, researching into the setting first certainly isn't required or anything. Though I wouldn't want to dissuade you from doing it, since obviously I think it's a pretty great setting. If you do want to do that, I'll do my best to get you the info once I catch you on AIM. In case you might happen to catch me first, though, my AIM's in my profile. Or you can use that button right below this sentence somewhere.