2001 E39 Failed head unit upgrade

[Obather12]

So I was ill advised by crutchfield in upgrading my head unit to an Alpine ILX650 as it's not compatible with the factory system...the entire system will apparently have to come out. Does any one have any advice or can point me in direction of a trouble shooting thread.

I'm prepared to replace the entire system but this particular model comes with a very good upgraded factory stereo already. It only needed bass and a new head unit as my pixels are dead. Any help or direction would be appreciated.