Fishwish,
You're not alone. I encourage you to keep at it, but remember mistakes will happen. That's part of the learning process. Some mistakes will be more depressing/expensive than others.
I'm in the process of setting up a 90 gallon AGA. To sum up my story...I bought a complete 75 gallon used setup minus the livestock for $1200. It included lights, protein skimmer, sump, return pump, wavemaker, RO/DI and basically everything else the guy had.
That was in March. I ended up throwing away the 75G tank because the plumbing was cemented in place and was leaking. It was also convient excuse to upgrade to a 90 . The CF lighting was crap and making a lot of noise so I ended up paying around $600 for T5 lighting. I've also blown money on plumbing parts I ended up not using.
I've lost a lot of money, but I've also learned a lot. You just need to go slow. I started in March and all I've got in my tank is liverock and sand. Sadly, I still stare at the tank for several hours a day.
Your perseverance will be rewarded.