I got some old flash units (e.g. Metz 30bct-3) that I won on eBay along with some older slr cameras. The flash units are in good condition. I thought of using them with my Canon 600D but heard about frying the camera's chip. Someone told about hotshoe pc sync and wireless trigger. I have no idea about these as I have just begin playing with dslr.
How do I get these old flashes working, either via wired or wireless, with my camera? What hardware would I need to accomplish this? What are the advantages and disadvantages of using an old flash unit with modern dslr camera?