Originally Posted by Spike100

It would be very difficult and expensive to install the OEM navigation system into a Z that wasn't built with one at the factory. If I remember correctly, the OEM navigation uses gyros (or at least one) and at least one GPS antenna. These parts are buried deeply inside the car. It's likely that after spending more than you already have in the parts, it won't work properly.

Some other points to consider:
1) If it's from an 03" as you seem to indicate, it's now 4 years old and may benefit from an updated navigation DVD disk.
2) There are better navigation devices available, and they are designed for simple fitment into a Z.
3) The Z's OEM Bose components are low-end and deliver poor audio. The amp is too small, and the speakers are poorly constructed.

I think a better choice is selling what you have and using the $$ to purchase good aftermarket stuff. You can probably find buyers who need to replace the factory stuff for one reason or another.
--Spike