no need for apologies, but you NEED to have your phone before you get apps. also your phone comes with an app called "Market" in which you can browse according to category or just search keywords. you can also shift between free/paid and New/updated apps
what you can do, if i'm not mistaken, is go to appbrain, login (if you have gmail, you are good to go), then you can pick out your apps beforehand. Then, when you get your phone, get appbrain from the marketplace, and you can sync it with what you picked online and you should be on your way.
yes, just as rsen said above. you can setup all your apps on app brain. youll have to setup a gmail account as well. when you get your Droid X you can setup the gmail account, then get the app brain application on the phone, then you can sync up all your apps