I remember when I was a young engineer. I got promoted through the ranks quickly, and at some point faced the same quagmire as you. What I ended up doing was to take a program of marketing management. Two months, Friday all day and Sat mornings for a month and a half to get a taste of the discipline (I was exposed to economy and accounting at the University, 12 weeks each, and lots of reading on economy, administration, etc). After that brief and non compromising stint, I realized that there were more nuances to marketing than what could be anticipated, and that the whole "Business" field was VERY interesting to me. Therefore, I went and did a full time MBA.
If you are gonna learn on your own (which I do not recommend), try to read the classics, Kotler on marketing management, rice & trout for positioning, etc. No Wikipedia or "Business for dummies" for you.
If you are going to take (a) short course(s) on the subject, go to reputable schools (I did the Short stint at IESA, not high in the world rankings, but best in my country, and did my MBA at IE in Madrid), while there are no hard and fast guarantees, going to reputable institutions will raise the possibility of being exposed to great teachers. Try to go for classroom courses, is harder, but you will build your "networking thingie" much better.
There is no guarantee that doing an MBA will improve your situation. But it would be hell to sign up for an MBA and discovering that you HATE "Business", and ALSO it would also be a grave mistake to decide "What you want to do" without at least a glance of what this "Business" thing is all about.