The tank can be the same, unless there has been copper medication used in the tank. If you are going with a sump/refugium, which I would recommend, I would get a reef ready tank, which means it is drilled to drain into a sump/refugium. The differences I found are great. I started with fresh water myself and found that it is so much more involved. I liked that. But very expensive and without a lot of research you are going to waste a lot of money. Live rock, protein skimmers, corals, fish all cost a pretty dollar in sw
aquariums. Even the water and salt mixes. I had a budget but realized very quickly it should have been higher. I would also recommend an RO
unit for your water. There are ways to keep the costs down but you don't want to go so cheap as too jeopardize the livestock.
Lots of great people here at this website but you need to do a lot of research and take your time and do it right the first time. It was at least two weeks before I had water in my tank and then another three weeks of cycle before I even put my clean up crew in there (crabs, shrimp, snails). Take your time, ask lots of questions, read, read, read...and then read some more.