Lucy,
I second David's recommendation of Alien Bees. I've been shooting with them since 2001 and they've traveled all over the country with me. I've never so much as had to change a flash tube.

Before you invest in studio lighting, however, you might want to see what you can get out of your current equipment in a studio setup. You can buy lightstands and umbrellas fairly inexpensively and mount your strobe so it bounces off of the umbrella in a single strobe setup. I believe the Nikon wireless system allows you to do it so you get TTL exposure as well even if you're bouncing the light.

Getting good with one strobe is a great way to start. Later, you can either get another Nikon strobe and use two in a wireless setup or migrate to a pure studio setup with two Alien Bees. I believe that James uses Canon strobes in a similar way when he does location shoots so maybe he can lend some advice.

I find that lighting animals in a studio environment is easier with two lights because I shoot a lot of black dogs. But often, I use the second strobe as a fill light while using the main strobe for primary exposure. With one strobe, you can use reflectors for fill.

The key is to do some reading, figure out what you really want for a studio environment and then start shooting and gaining experience. With digital, you get to see the results immediately and make corrections so there is less of a need for a flash meter.

Jim