Update:
Solved 2 problems:
WiFi works now, with the Broadcom BCM94321MC Card (I had to left the black cable unconnect)
Loaded EDP Files from the internet with SnowLeopard and WiFi working.
Aktually I am downloading Software Updates from Apple and posting now out of Snow Leopard (Yeha!)
But there is still the problem with the wrong display resolution left.
Hope some of you quys can help me.