Your facebook name is permanent so choose it wisely.
Your Fan page URL is going to be the one you see in the address bar when you go to your fan page. It is LONG!
Until you get your 25 fans you can either do a redirect through your hosting account or you can get the memorable
web address app from facebook. Either way is great.
You can also get the twitter app from FB apps and it will automatically update your twitter when you update your FB.
Another option is ping.fm. With Ping you can do all your networks (FB profile and fanpage, twitter, myspace, LinkedIn, etc) at one time. Just make sure that you don't have something hooked in to them that will automatically update them again because then you will have like 3-4 updates of the same thing. Another thing I like about ping is that you can use the email address it gives you to schedule your updates through outlook. One of my clients has a gmail account and so I have to use another tool to schedule theirs.
There are many tools that you can use for your social networks. I would suggest that you look at them and see which you like better. My tools for mine are ping.fm, hootsuite.com (I have all my profiles for twitter in there so I can monitor them all at once), and Lettermelater.com (the tool I use to schedule my clients updates that use only gmail).
If you have questions you can get me on yahoo, if i have confused you.