Wow... I'm jealous!
While folks have hinted around at it, if you want to go saltwater with that tank I hope you didn't spend all your cash on the down payment for the house! If you're looking at doing your biological filtration using live rock, as loyalrogue mentioned, the $1000 he threw out was a bare minimum price if all the planets aligned, the phase of the moon was just right, blah blah blah. If you bought that much rock at a LFS
, you'd be looking at $1500-1800 minimum.
I'm not trying to scare you away or anything. That'd be one cool saltwater tank. It's just that the "stuff" that came with it is pretty worthless. That biowheel... unless the hand holding it is that of a giant... is only rated for about a 20 gallon tank or so! And even if that one heater mounted in the corner IS working, I think a single heater located where it's at is going to have a problem keeping that tank warm no matter what the wattage.
Is the room that tank is located in heated? Looks like it's an unfinished room, and there's no insulation so I'm assuming the heat from the house can get back there. But if not, you should consider keeping that room heated once you get the aquarium going. That's where most of your heat loss is going to go, so if that room stays at 60 degrees or something, you're really going to be giving your tank heaters a workout and will have to be sized accordingly.
If I was you, I'd drain the tank and give it a good cleaning. You have no idea what may have gone into that tank (cleaning solutions, copper medications, etc) and if you're going to make a go of it, you should start from scratch knowing what you're putting in it to start with. With that big of a tank and that much money going into it , I wouldn't risk anything. As you're cleaning it, I'd probably also paint the back and sides of the tank (on the outside!) so you can't see through the tank and into that extra room (storage?). Just a personal preference, but something to think about.
Before you even set foot in a fish store or buy a single bit of equipment, I'd go out and buy "The New Marine Aquarium" by Michael Palleta. Read it cover to cover. After that, pick up Bob Fenner's book "The Conscientious Marine Aquarist" and skim through that. Palleta's book is a good intro with tons of good info, and Fenner's book is a bit more detailed and better to read 2nd once you're starting to get the idea.
You'll find tons of conflicting information, but just think things through and decide for yourself what you want to do. Understand why people hold the opinions they do, and be your own judge. Just like any hobby, you'll find as many different ways of doing things, or as many different "right" ways, as you have people.
Have fun, and start reading!