Some progress. I've added to /etc/rc.M
echonl "Starting ipw3945 daemon..."
after the hostname and nameserver section, and before the other networks section, and this seems to work all right.
I've uncommented a section in one of the rc scripts which starts inets, can't remember which one now, possibly the next few lines of /etc/rc.M. Not sure where else this might have been started from when this was commented.
I've also inserted the right values in /etc/rc.d/rc.inet1 and /etc/rc.d/rc.inet1.conf manually.
Then in /etc/rc.d/functions-network I've put
iwconfig eth1 essid "My_Network"
iwconfig eth1 key <mykey>
after the ifconfig lines (so eth1 is up before the iwconfig commands) and just before the gateway is probed
This works, but produces an error message because these iwconfig commands also get run while eth0 (the NIC) is getting set up, (before eth1 is set up).
Still not the way it is supposed to go but never mind.
There are further lines in functions-network referring to wireless interfaces but I wasn't sure what difference it made that my wireless interface is called eth1 and not wlan0 for how to edit this part.
Feel like I'm getting warmer but if someone wants to tell me where these changes really belong I would prefer to know how VL was designed to start.