I'm thinking of moving my social network from shared hosting to VPS hosting. I'm not familiar with VPS and have no experience. Will that be a problem?
If you're familiar adminning desktop systems with the same OS as your VPS, then you'll be spared the biggest shock that comes with VPS. VPS is to shared hosting what (remote) adminning a system is to having a user account on that system.
Things you have to worry about with VPS that you didn't have to with shared hosting:
The good news is that running a web server shouldn't look much different, in my experience, after the move, except that you can change some things faster because you don't have to ask anyone.
If you enjoy looking after boxes, you will find a VPS much more fun than a shared host. Try running an experimental VPS for a few weeks before you commit anything to it.
Depends. Shared hosting everything is setup for you (Apache, MySQL, PHP) and you normally have a nice frontend (cPanel) to deal with setting up databases and domains.
With a VPS plan it would depend on what it came with before you could estimate the work involved. Obviously you're going to have to move any files and recreate the databases, but you'll also want to double check the versions of PHP and MySQL they have installed. Most VPS plans (if not all) give you root access to the server so you'll be able to customize it to whatever you need.
When I went to a VPS solution I went to SliceHost. For very little money (and no contract) you get a bare Linux install to play with. You have to install and setup everything by hand. You don't have a cPanel / Plesk frontend to do it all for you, though you are free to install one if you wish. I preferred this approach because I wanted a more hands on role in running the site.