it is a very easy install for the pac unit i actually had to install it twice after my first head unit took a dive. i removed it and sent it back got the new unit and installed it in there and no problems. the directions are pretty straight forward.
on the other hand the avic-z1 is also a nice unit but you will have to bypass some things if you want the unit to play when not in park.
check out this site
http://www.avic411.com
you can find some great info on all the pioneer units