My Linux experience is confined to Libranet 2.8.1 (kernel 2.4.21), a distribution that is no longer maintained. It seems to be based on Debian "sarge" but has a built-in administrative system for downloading applications or modules, making it easy for beginners like me. Now I have just obtained high-speed DSL and my question is whether it is foolish to get updates of applications and Debian to add to my Libranet system. Perhaps that is just asking for trouble. Or should I instead forget about Libranet and start all over with Debian "etch" (the newest stable Debian I believe) or some other distribution? An experienced answer to this question I am sure will save me a lot of pain.

Debian Etch has an automated system to check for updates. (update-notfier)
Debian Etch has a GUI Package management tool for installing new applications. (synaptic)
Debian Etch has a Graphical installer now (installgui)
It's really not hard to use, imho.

If it were me, I would backup my Data and do a clean install of Debian Etch..

In addition to just Debian [etch], that functionality (automated package management with graphical front-end, ...) is implemented in almost every newish distribution of GNU/Linux. That means whatever distribution you install, probabilities are high that it has such tools for you. Ubuntu, based on Debian, has come very popular for it's easiness - it uses mostly the same tools that Debian does, and in addition has (as an example) a graphical Add/Remove tool with which it's easy to install and remove pieces of software from the internet with just a couple of clicks. Synaptic and such are there of course, for more "advanced" things.

SuSE also has it's YaST, Fedora has it's own (yum-based) graphical tool to manage updates and so on. So instead of making your life difficult, I second what farslayer said: it's easier to backup the data, get a new distribution install disc (Ubuntu and some others offer a live-cd; Ubuntu's Desktop Edition is a combined live-cd that you can test before installing, and install-cd (dvd) that you can install the thing from) and make a fresh start. Whichever distribution you choose, it's not difficult nowadays. SuSE and Ubuntu hold a reputation of being (also) newbie-friendly, and I - having tried and using several distributions over the years - can't say much bad about it. It's what Debian offers and a little more, but if you want to take the "100% pure Debian" route, go ahead - it won't harm you.

Thanks, farslayer and b0uncer, I'll follow your advice when I figure out how to do it. Curiously my new Verizon DSL works just fine on Linux despite all the problems I read that others have had setting it up. Hope it still functions when I replace the distro.