You are not really converting your pool if you already use chlorine. You are merely plumbing in (and wiring) a SWCG and adding enough salt for it to make chlorine for you. You can continue to use various forms of chlorine without any worry about "compatibility"....it's all chlorine.

As for cost: There's no set cost. You can get inexpensive systems for a few hundred or spend thousands. Even saying $1500 is "typical" could be misleading.

While SWCGs are great, they are not a cure-all. You still need to test and watch your pool, but you CAN (when it's good) take off for a week or two without too much worry. And, if you learn the B-B-B system thoroughly (which is pretty simple) the SWCG will simply make it easier.