According to me there are 2 ways:
Option 1: Hire an animation company to produce a movie on your story, this would be a little easier than Option 2.
Option 2: Start your own production, hire artists etc. This will be full self-production but would be harder to achieve.
If you hire a company then they will/may mostly charge you on per second basis. Rates may vary from company to company and the output of the film(2d/3d).
If you decide to setup your own production then it will cost more as you have to get a location for your studio, production level PCs, artist salary etc.
You could also try selling your script to a producer(if he accepts scripts).
I don't know about marketing so can't comment on that