What system would I need if I want to store large amounts of text data and be able to control a TFT LCD display?
You need an microcontroller IC, a display, and a mass storage device. For your application, an SD card would be a good choice for the mass storage. Some microcontroller cards have an SD card slot built in. But if they don't, most microcontrollers have an appropriate interface. SD cards have several interface options, but for a microcontroller, the SPI (Serial Peripheral Interface) is probably the best choice.