Currently have a D1 in my 06 vw GLI if i decide to throw some cash out the window and pick up a z1 can i use all the existing wiring and install stuff? what about the trim rim that i fabbed? same size and what not?

The size is the same, I'm pretty sure you can re-use what you have for mounting. As for the wiring harnesses, I'm almost 100% positive that some guys did that here and they connectors are different. You can cut off the pioneer wires that came with your D1 and hook the new ones that will come with the Z1, but it's not just an unplug and plug in the new one.