RepRap Data Communication

I am thinking about building a RepRap Prusa Mendel (3D Printer). My biggest worry is the electronics. I will use RAMPS 1.4http://ultimachine.com/ramps-pre-assembled-kit-complete to control it. It is essentially an Arduino Mega shield. It would help me decide if someone could explain how I would actually send a file to print. Hopefully someone here has tried this before.

Thanks in advance.

The Arduino Mega has a USB-B conector at one end. You run a USB printer cable from your PC to your Arduino and communicate with the board as if it were on a serial port.

It would help me decide if someone could explain how I would actually send a file to print

In exactly the same way as using any other electronics with the RepRap. A program on the computer feeds the bytes from the file on at a time to the serial port. Most people use things like Replicator G to do this but there are many other programs that do it. You can even write your own if you like. I wrote one in the Processing language, you can get it here. http://www.thebox.myzen.co.uk/Hardware/CNC_Conversion.html