Hey Saltwater Teen, these guys are just trying to help you here and I am sure that we can get you setup nicely. Nick and others are a little frustrated because you took the time to ask a question, but are not taking the time to help them help you.
I will try to explain a couple things to you to help you understand how everythign works. The way a sump system works is as follows: Your main tank has a overflow installed, what this does is as the water level in your tank reaches a certain height it 'overflows' into your overflow and this water gets routed thru drainage plumbing down to the sump. What this does is it keeps a constant water level in your main system. There are several different types overflows that all work, some are better then others. Like nick stated the best way to go is to have your tank drilled, this is done by a glass shop or certain local fish stores. This is not always a option for everyone due to tanks being setup already. It usually costs about $30 to have the hole drilled for you. Now option b is to use a overflow that operates off of a siphon. These do work and with regular maintenance are a pretty safe option. What these do is they have a small box inside the top of your main tank, and a small box mounted just on the opposite side of the glass with a siphon tube connecting them together. Anyway the water flows down the drainage pipework into the sump via gravity power, and then flow thru a series of dividers/baffles to keep the bubbles down, gets skimmed heated and everything else. Then it gets returned to the main tank via your return pump. Once the water gets returned to the main tank it the causes the water to overflow and it is all one big happy process. I would go w/ a mag 9 or 12 if I were you for simplicities sake. These pumps can be run internal or external, and what that means is how it is mounted in relation to your sump. A internally mounted pump would be actually submersed in the sump with the plumbing going right back to the main tank. A externally mounted return pump is mounted externally in relation to the sump, and has a hole drilled w/ a bulkhead in the side of the sump gong to the intake of the pump, then the output is plumbed back to the main tank. There are advantages to both styles, but internal is simpler and easier to go with for beginners. So once you have your overflow taken care of you can then worry about the sump. I would listen to these guys here and save a ton of cash!!! It really is simple to create you own sump from a old glass tank. We will lay it out for you with measurements and diagrams to follow. I am sure that if you absolutely are not able to handle it, someone would be willing to help you out with this. (I will help you if you can wait for a couple months for me to get back in town and I am right down the road from you) I would not recomment that sump from etss because the skimmer is not what you want, trust me on that. I would look to ebay for a euroreef es 5-3, this would be a fantastic skimmer for your setup!
Anyway just some food for thought, and we do want to help you out. You definately have some researching to do before you go out and order anything. No need need to rush anything here.