I have some experience of writing short film scripts, radio plays and corporate videos at a media student level.
Like you I have a talent for this kind of thing.
The facts are as follows,
If your idea is good enough then Hollywood agents will fight for the privilege of selling your script for you to a producer for ridiculous sums of money, ridiculously large that is. The reason for this is simple. The overwhelming majority of scripts that are presented to producers are very poor, and that includes some of the ones that actually get made into films. Really good scripts will make millions.
If you don't know the correct format with which to present your script they will simply pay a script doctor to whip your script into shape, it is the idea that counts and the quality of the script, not the format it's in.
You do not need previous training to become a good script writer but if you do have some training it will help. I trained in advanced media studies and communication. I also directed, acted and produced at a student level and that is also useful.
Although you do not need training, you do need more than a natural talent, you need to know how to write a script. That means how to arrange the plot, how to create realistic characters and story lines, how to create the right pace, tension, feel etc etc etc. you need to know how to avoid cliche, how to provoke viewers emotions, how to draw people into your story etc etc etc. There is a hell of a lot to learn and if you learn it all you also need other things.
You need to be in a position where you have time to write it. The idea situation is if you have no children and live with a woman who keeps you, then you can dedicate yourself totally to your task. If you can not place yourself in that position you have to be as close to that position as possible because if your task as a non experienced and non trained scriptwriter is to do that which hundreds of thousands of trained and experienced scriptwriters often fail do. eg write an exceptional script that will make you a huge amount of money you have to pull out all the stops.
To achieve this you are looking at total dedication for maybe a couple of years. No going to pubs and clubs, no other hobbies, neglecting your girlfriend who will have to do all your cooking and washing because you will be too busy.
If you can put all that in place then all you have to do is to learn how to actually write a script and that is simple, not easy but simple.
Just buy a book that will tell you all you need to know. There are thousands of them available and most of them are simply not good enough. There is one book I know of however, that is exceptional and will tell you everything you need to know. Read it, learn it and do it and you will make money at it. The book is called:-
STORY by Robert McKee
This man also does seminars on the subject in UK and USA, here is a link
http://www.mckeestory.com/