Say I prove an identity that's quite important; important enough that an uneducated person like myself could get it published (given the proof is correct, of course). What then is the best course of action?

I am scared of sending to a publisher, because if it is wrong, perhaps that will set my potential maths publishing career off on a bad start? Perhaps the proof is hilariously bad? This is something I'd like to avoid... so, what about asking if the proof is correct on MathOverflow.SE or Mathematics.SE? If my proof is correct, then I'm pretty sure it'll be quite attractive. I'm scared that someone could steal it, and I don't know how easy it is to simply prove I made the proof by referring to the SE post. Perhaps I'm overthinking it, but if this proof I've made is actually correct, this could be the start of a mathematical career. I want to do it right.

Of course, there is rigorous checking that I could do myself. However, this identity is somewhat sizeable, so doing it by hand is bothersome and prone to error. I don't have Wolfram Mathematica, but I do have Wolfram Script; it is however only returning the input as the output, implying to me it doesn't know how to evaluate it.

So, how should I go about this?