You got an excellent deal on the Z1. I bought mine used for $900. I know I could have found a better price if I looked hard enough. You can download the manuals if you really need to. The deck is intuitive enough that you can figure most of it out on your own. That is, assuming you've had experience with after market head units.
I was in the same situation as you were in. I was debating between the Strada and the DNX7100. Car Audio and Electronics selected the 7100 as one of their products of the year. There was a comparison a few months ago and they gave the 7100 an A- while the Strada got a B+. If you look on CNET, the Strada scored higher than the 7100 by the editors. I almost got the Strada, but I was turned off because there is a 30GB HDD that does nothing but keep map info. Plus, there was no option to add a remote (I prefer to have one). The 7100 has an excellent Nav, but the GUI and menu system has a steep learning curve. Plus, the 2GB memory (I believe it's and SD card) didn't seem as adequate as the 30GB Z1 and Strada.
I lucked out and found a Z1 on craigslist, so I picked it up with a quickness. So far, no regrets. The maps are outdated, but I plan on doing the Z2 upgrade sometime soon. I think this forum has done a lot to add value to my purchase.
Thanks.