Hi Kristoria -
First of all, as someone mentioned upthread, if you haven't been there yet, check out the Whitney Portal Store Message Board:
http://www.whitneyportalstore.com/forum ... d=1&page=1
Search the forum as some of your questions (such as gear rental) have probably been answered. Check for weather & trail conditions as you approach your climb. Introduce yourself, see if other folks may be in the area when you are. They are very friendly and Whitney is pretty much all that is spoken there.
For better or worse, chances are you will meet up with other parties along the route. Folks on the MR (unlike the MT) are the sort that will let you climb with them, if necessary, give you a hand.
I've only been up there once with a group, I'd solo it now. Now that you've said sleeping bag, sounds like you'll be lugging an overnight pack up to UBSL or Iceberg. With a big pack, solo, the Ebersbacher Ledges might be the crux of the climb. A photo link from someone on the Whitney forum:
http://www.flickr.com/photos/rockwellb/ ... 322219631/
A little navigation is required. If the ledges are wet, yikes, you might want to haul packs, hard to do on your own. But we've had a good dose of snow this year. On your target date, you may be able to bypass the E-ledges, rather plow straight up the creek. If there's enough snow, the bushwhacking isn't too bad. For me, at least, that section would be the mental crux, the rest is just a slog.