As long as you can still get the card for that camera it should be fine. Nikon is the best IMO. I use the D70 and love it. I have a nikon 60mm 2.8 lens and it takes fabulous photos. Get good glass. If you go with an aftermarket lens go with Tamron, otherwise get a Nikon lens and get one as fast...
Buy from a reputable site. They will most likely carry quality products. I have XM at the moment and like them. Look at this page...all these brands are good IMO... Metal Halide Lamps - Single Ended - 250 Watt
I don't think that is enough but someone more knowledgeable will chime in. Clams need lots of intense light and I know it can be done with T5's but I don't think you have enough of them. If you had six bulbs I would say yes for sure. With four...it's iffy.
A Turboflotor is a good skimmer at a very affordable price. Unless they changed the design it can be used either in sump or hang on. I used one and was very pleased with it. (I got a much larger tank and had to upgrade)
Aqua Medic Turboflotor T1000 Protein Skimmer
It's hard to say for sure. They need lots of light so move it higher may help. They like flow, but not to much flow. Situate it so it is waving, but not being blown to bits. I don't have my links to iodine dipping on this computer so maybe someone else will help there.
It looks like you have all the parts. Ballast, endcaps, wires, a fan and a canopy to hold it all. I would ditch the LED's. unless you just like to look at the tank at night. The fish don't need it. There really isn't anything to building the light system.
I bought mine from Premium Aquatics |...