You have to upload a ftp host, use this. Just transfer via serial (to /var/hack) and execute. Use any ftp client you like, no username password necessary.
Execute this program with > /dev/null & tacked on the end so you get your bash prompt back. The program will continue to run in the background. Auto execute from /etc/rc.d/rc.sysinit if you like, just after your turbonet stuff.
Instead of windows telnet, use Teraterm (it supports both serial and tcp/ip connection), just click File, New Connection and choose tcp/ip and enter you dtivo's ip address. But use ftp to transfer files instead of teraterm in ip mode. In case you don't have it, Teraterm can be foundhere.
Renaming your ethernet interface will have no adverse effects. And setting your default gateway to something phony (0.0.0.0 for example) is a good idea to keep it from "calling home".
Another hint, you can edit files on your pc if you use a program which can save files as unix files. I like Textpad, which can be found here.