Scubanurse,
Welcome to the world of diving!! Buying a BC...or any dive gear for that matter...can be frustrating. You...the buyer...will find it is a very controlled environment. If the store carries Brand A, they will not be allowed to carry Brands B and C and so on. It causes the buying public to have to drive around to many stores and see what they have. My BIGGEST piece of advice....buy your BC (and all life support gear) from a local store. And, be sure you register all your equipment. Things your life doesn't depend on can be bought on the net. (I can hear the yelling and screaming already!!!)
As for BC's, there are basically two types. Those that are vestlike and the bladder envelopes you.....and .... those that the bladder is all in the back. Both have advantages and disadvantages. The former (vest) is often accused of having more "squeeze" than the latter. The latter (back) is often accused of throwing a diver on their face while on the surface. The best thing to do is find a store that has a pool and will let you try each kind out...with a tank...and see what you like most. I would recommend a weight integrated system...that uses no lacing. Either velcrow or the new clip system. BC's will normally require a yearly servicing to keep the warrantee.
Good luck and send me an email if you have any other questions. I will be glad to share what I have learned on equipment buying with you. (rdr5k@yahoo.com)... good luck!!!