Could you elaborate a bit on how you learned sales by your self? Did you just start cold calling? I have no experience in this kind of thing what so ever and I think advice from someone with a similar background who has done it would be helpful.
I think the first step is demystifying it. If you wanted to learn a new programming language, you would just "do it": read books, read about the language, practice writing code, etc.
Compare that to a business, where you have to pay to file paperwork that you may have to hire a lawyer to tell you that you did wrong.
You need to know how to structure an articles of incorporation in a good way for your organization, and you only know you get it wrong when it's too late.
You need to know how to raise funds in a way that own't personally bankrupt you.
You need to know how to read and understand contracts.
You need to know how to hire people in a way that doesn't expose you unduly to lawsuits.
You need to know bookkeeping well enough so that you don't need to hire someone for that right off the bat.
There are tons of things. I know that I don't even know how much I don't know, because I've only ever had a small rinky-dink business.