TCWORLD:
And can the arduino read data from an external data source (there isn't enough to ram to store one frame on an arduino) and output the 24bit of colour data (or even 1bit) in 1 instruction clock?
Why does all this have to happen in 1 instruction clock? ronalda's planning to make a GUI interface for a thermostat, not a high-end graphics workstation.
As long as you can write to the driver during a given clock tick you can change the output of the display. The read time from the source file and any further processing aren't barriers, no matter how long they take the display will just stay at it's current state until given something else to display (the driver IC must have a system buffer of some sort, there's no way it's processing every pixel in parallel!).
The real time-related issue of concern is the refresh rate, long as the display is updated faster than ~24 frames per second (fps) most people won't notice delay for video. I'm not suggesting that an arduino could pull-off those refresh rates with this display, but rates of single digit fps seem possible. Unless this project includes live video feeds of ronalda's heater and AC equipment, even a few fps would probably be sufficient.
Again though, this is not something a novice should try cutting their teeth on, that's one of the reasons why I mentioned using an LCD. Not only could a monochrome text or graphical LCD do the job, there are many that already have Arduino tutorials and/or compatible with exisiting libraries. Also some are rather inexpensive if you don't need them to be very big, e.g. the 84 x 84 Nokia 5110 graphical LCD is ~10.00 USD at either Sparkfun or Adafruit.