I am running a network of 6 computers on three different opperating systems,
all on an Airport Extreme hooked up to DSL. I did an archive and install
from Tiger to Leopard, checking the checkbox that said to preserve users and
settings. I had absolutely no problem with my network before, during or
after the install. This isn't to say you shouldn't back up; it's just to say
that it's very likely you won't have a problem with this issue. If you have
an external firewire drive, you could use a program (I used superduper and
the free unregistered version works fine for this) to backup your entire
system to the point that you could actually boot into that system on your
firewire drive. If you aren't able to do that, I'll leave it to the more
experienced people in this area to tell you exactly what files you should
back up.
Hth.
--
Cheryl
"Where your treasure is,
there will your heart be also."