helping out a friend, he wants to get a different head unit.. right now he has a stock head unit

to me it seems pretty simple.. just pop off the panel and switch out the wires..

but that truck has a huge radio and he wants to get a touch screen one, with usb, ipod cord etc..

anyone have a suggestion on a good hu for this truck..

also.. he has just one sub in the back.. i believe one 10".. should this effect the wiring to the next head unit?

thanks