You'd be fine with keeping your live rock you have now, and perhaps adding more if you upgraded your tank.
As for the lights, same thing as szwab said. It all depeneds on what you plan on keeping AND your budget. As for the sump. I'd suggest a sump/fuge all in one. A great place to keep macroalgaes, heater, skimmer, etc.
You can look in the DIY forum and see how people have designed theirs. I would possibly think about using your 55 gallon you have now for a sump/fuge. Just go to lowes and get either glass or acryllic, silicon the baffles in, get a return pump and do the plumbing, and you'd be good to go.
Stewie