I solved my former netatalk problem. Looks like netatalk and LPRng don't go together unless you put a ":pr=| lpr -Pprinter:\" into the papd.conf file.
But now that I can print to my DeskJet 520 from my Mac I notice that the margins don't fit. I have yet to see a document that appears on paper the way it was intended to. Can anybody help me there? I use Debian 2.0's magicfilter package and LaserWriter driver 8.5.1 on the Mac. The PPD files are for Apple's LaserWriter II NT.