Yeah, you'll be fine for lights. Are your nitrates and phosphates zeroed too? If so, I'd say just go for it. One important thing though, make sure you check out the clam's foot on the bottom when you buy it. If it's torn, they seldom are able to recover from it and will probably die.
Another thing, if you aren't supplementing/testing calcium now (i.e. don't have hard corals), you'll need to grab a calcium test because that's how the clam grows its shell.