If I change my sources to ~/slackware-12.0 and/or ~/slackware-current, remove all the vector sources and do a slapt-get -dist-upgrade will I wind up on slackware, or wind up w/ a broken system?
You'll probably end up with a zombie-VL/Slackware-mutant, with lots of packages that don't work anymore. If it still works at all... remember, not all packages VL SOHO has are also available from Slackware. All packages that aren't there... well I don't think the old ones will work too well, since a lot of important stuff has changed between Slack 11 (base of SOHO 5.8 ) and Slack 12.