Question regarding use of multiple weapons

Hi all......been moving on to the next part of this uber long modelling project of mine. And as always, I've got more questions. I've noticed that from the samples, blizzard modellers include weapons in the .mdx files. I've heard others speak about "alpha-ing" objects out......but I'm quite unfamiliar with this process. I'd like to set it up such that a single hotkey controls the currently selected weapon.....so hitting it will play a short animation to transition from one weapon to the other, during which time, the one weapon would disappear while another becomes visible.

My question, then, is this: If I were to make 3 separate weapons for my SEAL character (a primary firearm, a secondary firearm, and a knife) how would I go about making the two unused weapons invisible until called upon? Also, would I simply need to link a dummy object to the hand.....then link the three weapons to the same dummy? Any help from the better animators out there would be greatly appreciated. Thanks.