I have one and I have played it a bit with some lower-volume singer/songwriter type gigs. I would say, go ahead, shop around, and get the best-sounding cajon you can buy. Don't settle for the cheapest, because it will sound cheap. It should have a very open, deep bass note that does not sound like slapping a cupped hand on a board, and a nice, cracking, snappy snare sound in the corners. The tapa should sound and feel live and responsive. Some folks have talked about beating the cajon to get sound from it. That means that you're either playing too loudly or your cajon is not correctly designed to give off maximum effective sound.
Lessons wouldn't hurt anything, but a lot of hand drumming and set drumming concepts can be applied to cajon playing without any issue. If you frequently find yourself in lo-fi, low-volume situations, it's a nice option to have.