Generally speaking, you should always upgrade to the latest possible system that you meet the specs for, as long as you have no “must have” apps that do not meet the specs. Upgrades and updates contain important security improvements plus additional features.
That said, with the minimal RAM you have, you might be better off sticking with 10.6.8. You don't need malware protection as long as you're careful and do not download anything from anywhere other than the Mac AppStore and developer's own sites.
If you do decide to upgrade the OS, you can do that easily yourself. RAM is not that expensive, so most of what they are quoting you is labor.