You're about to start plunking down some real money soon, so I would recommend that perhaps you should do some more research on your new hobby first. Getting into (or back into) bikes is probably one of the best "hobbies" you could have picked. And its not as expensive as some other hobbies can be.

Look at these two sites and surf around the various bike resource links you come across, go back through the archives of this list, lurk and read this list for a while and you may find a lot of your questions have been answered.

http://sheldonbrown.com/fixed-conver...l#freewheelhub
http://www.fixedgeargallery.com/

It's always nicer to help people that have done a bit of homework first before they start to ask questions. Also keep in mind that there are no stupid questions, despite how some may feel. Good Luck, and welcome to the "community".