Oh, sweetheart ... I am an agoraphobic author as well (not a famous one, but still a writer) and I feel your pain!

First, let me say that reputable *agents* NEVER ever accept money up front from their clients, except for very small things like postage, copying costs, etc. (Mind you, a "book doctor" will take your money and fix up your manuscript, but they are not trying to *sell* your manuscript, just make it better so that someone will want to publish it.) For a really good article on what agents should and should not do and how to deal with them, take a look at
http://www.sfwa.org/beware/agents.html. (Unfortunately, their web site is under renovation at the moment, so for now, look at the cached copy at
http://216.239.53.104/search?q=cache...hl=en&ie=UTF-8 .) Of course, since you have already paid the money, you are stuck with this course of action for the moment, but you should really read the article for future reference.
As for how to promote your work while dealing with your agoraphobia ... I have done some signings at places like Barnes & Noble, and all I can say is that drugs are your friend. No, I'm not kidding. Xanax has gotten me through some very tough places and times. For a long time I was very anti-drug, and I just got worse and worse. I finally started getting better after I combined using medication (Xanax) and MADE myself get out and expose myself to various situations (including the signings I was talking about). The drugs made it bearable, and apparently some itsy-bitsy part of my brain realized that I wouldn't die if I got out of the house a little bit!

So I am much better than I used to be, though still not cured of everything.
So ... read the article. Get some drugs. Go to the signings in a nice outfit and wearing a smile. Get a different agent, if you can.
Good luck!!!
~ A foolish consistency is the hobgoblin of little minds.... Emerson