I updated gpg and ran slackpkg update. However, when I try to search for firefox it lists the upgrade from 24.1 to 24.5. Shouldn't the update list it for FF 29? Also, keep getting command not found.

Assuming that you run Slackware 14.1, the current Firefox version is 24.5. 29 is only for Slackware-current (that you shouldn't run, as that's for experienced Slackware users).

About "command not found", we can't help you if you don't tell which exact command you typed, and if it was as a regular user or as root.

Ah, got it.

When I wanted to upgrade, I put both versions of firefox (original and upgrade) instead of just the original in the syntax.

I didn't know that. I just assumed we all ran 64bit multi-lib current.( Seriously, I tell people to upgrade to current all the time to fix oddball problems associated with libs or new software releases).
Historically, I've run into a couple of issues but I just chalked that up to the Slackware Motto,
'If it you don't have to tinker with it, you aint tryin'.

Rationale:

• Main aim of Slackware-current is helping iron out future stable Slackware. It is unlikely that newcomers can actually help (though that probably happens sometimes). In any case it is not intended to be used in production.
• There is little benefit to run Slackware-current over Slackware stable, but some specific cases, like new drivers or software versions that fit a specific system configuration. But even then, the new drivers or software versions can often be backported to -stable, just rebuilding the involved package or kernel (module).
• However seldom, -current can be unstable at times. A Slackware newcomer will probably have more difficulties to solve such a problem.

FYI I'm running Slackware 14.0 at the moment and am perfectly happy with it. I occasionally run more recent versions, but only for testing or to provide stuff for these versions.

I'm working a lot in my free time with libvirt and qemu-kvm, I know they aren't in current but based on where I pulled them down from, I'd imagine they are on the table for future releases. On the whole they work extremely well on current, though I haven't started benchmarking the guest OSs' yet, I want to make sure I've fully explored the options for configuration and image creation before I worry about stability and bloat. I'm trying to keep copious notes as I work with them, for my own purposes originally but if they could be helpful, what should I do, just post them somewhere and leave a link here?

Yeah, you could do that. Or you could:

• Create a new informational thread in a relevant LQ forum.
• Make a new entry in your own LQ blog.
• Write a new article in the Slackware Documentation Project.

Thanks, the LQ blog is where I was thinking of posting them anyway, but I appreciate any direction I can get.
I don't think they'd be suitable for Slackware Documentation, not, at least until somebody else tries to repeat the steps and has the same outcome. Just the same, I'd like to contribute to the Distro in any way I can so any suggestions you think would be useful, I appreciate the time you invest in conveying them to me.
Creating a thread... I tried that once but the result wasn't what I'd hoped for. When I'm done with this side project, I'll try it again.