I've never tried to chisel marble but I'm guessing its not all the hard to learn. I'm also guessing that simply know how to chip at marble with a hammer and chisel isn't enough to create sculpture as fine as Michaelangelo, but that's where you start.
Film school plus years of practice, total determination, talent, contacts and some luck might turn you into a decent film director. Film school alone won't do it but that's where you start.
The basic techniques you need to know are surprisingly simple. Some of the top film directors have said they can be learned in a few weeks at most. If you want to learn them you don't need an expensive, top film school to learn them. There are many online film school resources to learn filmmaking.
Once you understand the basics just add total determination, talent, contacts and some luck.