I soon expect to update my Slackware 10.1/KDE 3.3.2 box to 10.2/3.4.3. A year ago I somehow magically managed to recompile the 2.4.28 kernel to provide some minor adjustments for my first box. Of course, when I update to 10.2, kernel 2.4.31 will be installed.

Back when I was toying for those few days I developed a habit of being careful about maintaining my GRUB menu.lst such that if a recompiling effort failed I could easily revert to a previous working kernel menu option.

But I never had two different kernel versions installed and this is new territory for me.

When I update to 10.2 will the sym link from /usr/src/linux be automatically modified from /usr/src/linux-2.4.28 to /usr/src/linux-2.4.31? If so, then how does that affect the currently installed 2.4.28 kernel I recompiled and installed?

What precautions do I need take to preserve my 2.4.28 recompiling before I begin trying to learn more about recompiling with the 2.4.31 kernel?

If I recompile the 2.4.31 kernel and update the module dependencies, and my effort fails, will my previous 2.4.28 dependencies remain untouched and usable?

I already maintain copies of my kernel, system.map and config file in my /boot partition and identified by a unique name such that any recompiling effort does not easily overwrite those files. I'm not sure how the kernel knows where to look for the modules, is that defined in the system.map or config file?

Anyway, like many of my questions, I'm once again looking for the big picture and the general concepts involved. Thanks again.

That link only affects the source, and will only be changed if you install another Kernel Source package. The link is really only a short-cut to the latest source you have loaded and isn't actually used when you compile a kernel, because you should already be inside that directory. As it's only a link to a directory, it won't affect your current kernel at all.
Copy the .config file out of the kernel-2.4.28 directory. That way you can use it as a base for configuring under 2.4.31, using make oldconfig (I think). Unless you plan on compiling another kernel under 2.4.28, then you don't need to "force" the upgrade to leave your old source tree.
If you only recompile, yes. But be careful upgrading the kernel-modules and kernel when you upgrade. You'll have to install those, not upgrade, or else it'll remove the old ones.
The lilo, or grub (I'm assuming) configuration files tell it where the kernels reside, and what they're called. The modules are in /lib/modules/<kernel version>

Cheers,
Eddie

Ah, that makes sense. So do not do a "blind" upgradepkg */*.tgz, or at least skip the kernel stuff when using that command.