Hello,
tough work, soldering this cable, isn't it ? But you get used to it. I made some of these in different flavours to keep some old macs alive and useful in a scientific laboratory. (They run instrument controller applications written in HyperCard.)
You might like to look for an scsi-ethernet adaptor (10BaseT) and hook your PowerBook directly to a router. The manufacturer Asante provides appropriate driver software, still:
http://www.asante.com/support/legacy/Bridges/EN_SC.asp
The following page gives some pictures and written information about this kind of device (German):
http://www.oldmac.de/netzwerk11.html
Different connecting cables were shipped with the adaptors. Be sure to get an appropriate HDI30-connector if you want to use this with an old PB. (Note: there are different HDI30 to DSub25 or Centronix50 adaptors available. Some are only for connecting the PB in disk mode to another computer, some are to attach scsi peripheral devices to the PB, some are switchable to either mode.)
There are lots of examples on how to set up machines like a classic PB for useful purposes (like a mail server). Have a look at the following pages:
http://servers.ld8.org/servers.html
http://www.fenestrated.net/~macman/68kMail/
Kind regards