You don't have to get discouraged. I also felt the same way, I just didn't know if I could handle all the work it took to keep the tank going. Just take things one step at a time and try to keep it simple as possible. Since you want to start up a 150 g, thats great, but I would try a smaller tank first, just so you can see whats its like on a smaller scale.
After reading this thread, I went and saw finding nemo last night, and yes you could keep all the fish from the movie together, except of course gill. I believe there is a type of butterfly fish that looks very similar to Gill, so that might work instead.
Also get used to mixing up salt water in buckets, except when first filling the tank. When you are ready for some fish, I would get the clowns first as far as fish go. Have your cleaner crew in before hand, and everything should work out. Once you get the hang of everything, it becomes easier and easier, and then you too will be able to give advice to others who are starting out just like you had. Make sure you research each and every fish, so you know their eating habits, what they like and who they get along with. Also do a search for compatibility chart on the web, that would be a helpful starting. Keep the questions coming and we will try to help in anyway we can.