That same can do attitude has haunted me through much of my life. There's never been something that someone else can do that I looked at and didn't think, “Anything you can do I can do better.” Some might call that conceit, but I think it's a great attitude to have in life, just so long as you don't let it go to your head.
I honestly believe that anyone can do anything they put their minds to. It's not that I think I'm amazing, it's that I really don't think that there is much that separates two people in what they do aside from the time that they've spent working on it. And there in lies our problem. Time.
You see, each one of these new tasks that I take on requires an investment in time. The question you have to ask yourself is whether or not the time spent learning something new would be better spent furthering progress in something you already know. Concert pianists don't learn their trade, get some diploma, and then stop learning and practicing.
If you want to be the best at something, or even noteworthy, you have to dedicate yourself to it. There is no special Jack-Of-All-Trades award presented every year. Thomas Jefferson might have been a great politician, architect, and thinker, but he only became recognized for the second two because of his dedication to the first.
So as you're getting ready to code and design your own website and blog, then quickly pick up Photo Shop so that you can design your book cover, and oh, while you're at it become a master at digital photography so that you can shoot all of your own photos, try to figure out how much of that time might be better spent on honing the craft of writing. You know, that thing on which all the others hinge upon.
If you have the money, it might be a wiser decision to find someone who has chosen one of those aforementioned fields and made it their own. Especially when it comes to marketing. Take it from a graphic designer turned carpenter turned writer turned. . . okay, so I don't practice what a I preach. Sue me. But wait till after I take the Bar. (Kidding)