Slackware ISOs
 

Which ISOs do I download? install.iso, extra.iso, or source.iso, or all of them? Will I actually use them all or do I only need one or two? Thanks in advance.

you'll definitely need install.iso. for most cases, this is all you need for a slack install.
the extra.iso is depends on each release. this is needed if you want some extra utilities, programs or something. i can't remember... i didn't get it ;)
the source.iso is if you're gonna do some hacking... usually not needed.

oh yea... and it'll be more helpful for you if you posted in the relevant forums. for questions relating specifically to slackware, there's a special forum for it under the main forum of distributions. the people there usually respond quickly. :)