Thanks to all the great advice I got on this list (especially from Ethan Benson). I managed to install Debian from the boot floppies on my 7300 without a problem (apart from quite a few errors installing some packages).
I have a friend who's about to switch from MkLinux to LinuxPPC, and who I'm trying to convince to try Debian. He has cable modem so FTP installation should be easy (I downaloaded all the packages I'd chosen in 13 minutes...), however he's using DHCP. I didn't see any option to use this from the installer (it's either static or PPP it seems). Is there a hack he could use to make this work? I was think it might be possible to temporarily exit the installer, go into a shell, get the DHCP package (previously downloaded on another partition), launch it manually and then go back to the installer. Would that work?