Welcome aboard!! Check out smokerplans.net, they should have a set of plans for the 500 gallon tanks that gives you all of the information that you need to build it right. You can definitely design it yourself using the smokerbuilder calculators and some help from the guys on the forum but it's nice to have a set of drawings and technical support if you've never built one before. Either way you go just be sure to post plenty of pictures along the way.
Learning generally boils down to "Repetition or the avoidance of pain", some people learn by doing, some by watching and some just have to pee on the electric fence.
Whether you think that you can, or that you can't, you are usually right. Henry Ford