A) You need a micro SD memory card for your Bold. If that is what you have, then you are good to go.
B) Yes, you can customize wallpapers. I am sure you can find a Tupac theme somewhere, if not you can always request for someone here to make one.
C) If you drop it in water you want to put it into a bag of rice for about 24 hours before turning the device back on. I would suggest you do everything possible to keep it away from water, though. It will void your warranty.
D)I am not sure if they have privacy screens out for the Bold just yet, but give it some time and I am sure they will have precut ones, if they don't already.
E) No, you can't use BBM as a text message. You can however use wifi, but that retricts what you can use. Do a search for a complete wifi guides on the boards.