OK. I'd like to retro-fit NAV into my car, BUT I don't actually want NAV

Meaning, I don't actually need the navigational system, but rather have the look, and the screen, which would be capable of portraying other goodies.

So, if I want to retrofit NAV, but don't need the actual GPS system, could I simply retrofit the screen, and still be able to control my stock speakers? I was thinking of using something like iLink, as wuzin has integrated here.

Sorry if what I'm saying is ridiculous, but thanks for any help in the right direction