Well, it depends on how familiar you are with programming languages in general. I started playing with Decal after one year of college with about 3 years of "professional" (defined as a paying job involving some code of some sort, not counting HTML/JavaScript/etc.) experience and picked it up just fine. I'd say if you're familiar with C++, Java, C#, or another .NET language, you should be able to pick it up easily.
Personally, I prefer using C# and Decal Adapter as it's easy to use and very quick to get something up and running. I'm sure that creates some overhead though, but I haven't seen any practical difference in speed between VB6, C# (Adapter), and C++ plugins. So I would say use whatever you're most familiar and comfortable with, especially if you just want to problem solve.
I'd check out the forums (http://forums.acdev.org) as well.
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We are like dwarfs sitting on the shoulders of giants. We see more and things that are more distant than they did,
not because our sight is superior or because we are taller than they, but because they raise us up and their
great stature adds to ours