Some things to find out first before you jump right into ripping into the dashboard are... Does the vehicle have any cable driven controls, electronic or vacuum lines, and to what degree of difficultly your willing to go to relocating and extending these things, the radio in my opinion would be the easiest to relocate you would just need to extend to the factory harness to reach your new location and figuring out a mounting solution for the radio and making a new or using the factory radio bezel as a template to build off of to create a new bezel in the relocated spot. As far as controlling the computers audio through the factory radio you could use the auxillary input if present or try and use one of those adapters to adapt the radio to have a set of rca inputs if possible.
In short, there isnt an exact way or any single way to do this, its much more of a trial and error method .
Snap some pictures so we can see what you have to work with.