help getting radio working when missing parts
 

So a couple weeks ago I bought a used x5 to fix up and use as my dd. Coming from a 540i I wasn't to worried about a bunch of the issues but the radio has me confused. I already searched but this isn't really common. The x5 has factory nav (4:3) and hifi professional. I have a screen and gps unit but the factory amp and cd changer are missing. The screen and buttons glow but nothing more. it looks like someone had a aftermarket amp and some boxes talking about aftermarket cd changers. I would love to install a headunit maybe a haulingan but don't know if it will work since I'm missing parts. Sorry for the long post thanks in advance.