Thanks everybody, I got it to boot into netbsd (the miniroot only).  I only had
access to a sun sparcclassic as my helper machine (it was the only computer with
scsi that I could get inside of).  My disk was sdc on the machine so I used
fdisk to create the /dev/sdc3 partition for the whole disk.  I then gunzipped
the diskimage and "dd if=diskimage of=/dev/sdc3".  After plugging it into the
DecStation 5000/120 the command boot 3/rz4a/netbsd" did not work (it is scsi id
4) however "boot 3/rz4/netbsd" did work.  Perhaps somebody could add my 
experiences to the installation guide (or I could if somebody would tell me 
quite what to do) in order to help others who do not have access to another 
working decstation or netbsd machine.  I still am in need of an aui to rj45
transciever.  Are they compatible with the mac transcievers?  Does anyone 
know where in cambridge mass I could find one?  

Thanks
--Eric