Well you have received a lot of great advise. I will wade in with my 2cents worth. I started off with a Cambo studio type 4x5 and love it. Still use it a lot and take it into the field when I'm not backpacking. You can get them for a reasonable price on eBay. The lenses I recommend are 90mm, 150mm and 210mm to start. Once you have mastered them you could look at a 75mm and something over 300mm. Get a Grafmatic back or two or three as it will make your life much simpler. I just got some and wonder how I managed without them.

Get some books, ask lots of questions and more importantly shoot lots of film. I find you can not think in the same terms as 35mm. Just becuase a 90mm lens in 4x5 is roughly equivalent to a 28mm in 35mm, it doesn't mean it "looks" the same in 4x5. Especially when you start to get good at using all the movements at your disposal in 4x5.

There seems to be a major resurgence of interest in LF. Welcome to the wave of the future!