Touchscreen project with Arduino Mega 2560

Currently I have an Arduino Mega 2560 with about 7 pins + SPI being used to control a couple digital pots and a 16bit ADC over SPI. I would like to interface a touchscreen display to this project about (5 to 7 inches big) that has a very nice menu that lets you set parameters and read the calculated ADC values to the screen. I'm am totally lost as to what the Mega 2560 would be capable of driving and however I do it I would need the menus to look pretty snazzy (maybe I can photoshop the buttons and menus and have the touchscreen pull images from an SD card?). Anyway any help on this would be greatly appreciated, thanks!

there is a image converter that you can get with one of the libraries for the arduino touch screen. I have a sainsmart mega with shield and touchscreen. the libraries work well and the examples work after some calibration. I paid £30 in total for the three boards. there are three libraries you can download, utft, utouch and utft buttons. each one has a couple of examples. its not difficult to show text. I am struggling with the buttons and creating a menu and different pages. there seems to be a lot available if you know how to get it working.

good luck and update your post with your findings