A small tank is really not the best place to enter the hobby. That siad though it is more than do-able. I have a 5.5 mini bow that does just fine. As far as your current set up, it will need to be stripped down and cleaned. The current substrate will need to be replaced with a good oolitic aragonite sand. You will most likely need a heater as well.
LR would be a definate plus that I would strongly urge you to get, about 5-10 lbs worth. Try to get smaler pieces as they will be alot easier to stack to your liking. The Whisper can be used to help with water flow but with the
LR, it does not really need any media in it. I like to keep mine on for the occassional polishing in which I find Polyfilters to work best. I would also get an additional powerhead. A MaxiJet 404 or 606 would work quite well.
Does the little tank have any lighting?
LR without coral additions can be easily maintained with
NO lighting but if your eventual goal is a mini reef, you'll need much more intense lighting.
Don't forget to <<
cycle the tank>> properly and be very chooseyif you decide to add a fish. It will only support one and very small adult size at that. Personally I prefer mobile inverts to fish for smaller tanks.
Other equipment you will need....
Refractometer (swing arms are too clumbsy on smaller tanks)
Basic test kits... ammonia, nitrite, nitrate and pH
Cheers
Steve