Server Question

I've never done anything server-related, but I'd look at grabbing the Server or Network Install version of your distro of choice, and then building onto that. They would be terminal-based at first, but that's nothing that then grabbing Fluxbox (or maybe xfce or LXDE, if you prefer less minimalism) from the distro's repositories wouldn't fix. I used Fluxbox a lot a few years ago², and it'll get the job done...but some of the problem is outside of the GUI - core services and so on take up resources, and that could even stand to slow down the *boxen choices.

²on a 1GHz Celeron Coppermine with 256 MBs of RAM...so more powerful than a PII (the Coppermine was a PIII core), but still in much of the same boat by today's standards. I went on an upgrading spree back in December/January and put in a graphics card and an extra 256MB stick, so it's a tad more beefy than it was then. The RAM wasn't actually all that expensive, considering the age/rarity of regular old SDRAM of the non-DDR variety.

Well, my only [substantive] experience thus far is with Ubuntu (although I am currently wrangling with Fedora 11 to figure out how to get darwinx working), but generally it would be something like:
yum seems to be a lot more finicky than apt-get, or maybe it's just that Ubuntu provides more meta-packages and aliases that don't require knowing the exact name of a package. I would first do (note: I'm more comfortable enabling sudo, but su can work if you're not wanting to mess with getting into/editing the sudoers file):
Double-check that it actually is in there, and then
And then you can go ahead and execute fluxbox. It could get tricky if it doesn't auto-configure itself, though, so you may want to at least manage to install a more robust environment first and then install Fluxbox later - that way you can switch between them in GDM or KDM (if you actually have a graphical login prompt).

You could probably see if the existing openSUSE install has Fluxbox in its repositories, and (noting that I have absolutely zero experience with openSUSE to know if it allows having multiple desktop environments installed at the same time), install it and see if an entry for it appears on your login screen. Then just choose to log into it instead of KDE.

Ok, Gnome then. Most SUSE users I've encountered go with KDE, that's why I used it in the example.

Give Ubuntu server a try. The CLI really isn't hard to get used to and once you're set up you'll rarely have to worry about it again.

For SUSE, you don't run apt. Instead, you can either use rpm or just run a simpler version of yast at the command line. Just type yast when logged in as root. The funny thing about the CLI is that if you don't have the correct permissions (i.e. root) it will claim the command doesn't exist when you're trying to type it in.

For your window manager, you can try fvwm. Of course, the main problem here is that you're using a very slow system for a web server. I would use a system like that for a home file/print server, but for a web server where all kinds of people are going to be logging in to see your site, something beefier is in order.

Lightweight window managers:
Fluxbox (Used this for awhile on Arch; liked it)
Openbox (Similar to Fluxbox)
dwm (VERY lightweight)

You don't really need a gui on a server it's a waste of memory. With only 256mb of ram you need to look at slimmer distros like puppy or dsl. They'll still do the job but they're optimized to work well on old machines like that.