Has anyone tried connecting an Arduino to a GPS touchscreen like a 4.3 Magellan. In my case I'd like to use it for displaying information about an EV conversion. One possibility would be a toggle switch that would switch between the GPS mode and Arduino for information about the electric car. In that case the audio turn instructions would still be heard while the Arduino is displaying the car's iinfo.
I'll have to say: If you have to ask, it's impossible.
You can run that kind of display with an ARM microprocessor, the Ardunio does not have enough processing power or memory to control a "dumb" graphical display like that. You need to push pixel data out at around 25 MHz to use that kind of display. So won't happen.