First off, your attitude needs some work, if you don't care about getting better you never will.
Second. You need to learn a programing language. I'd recommend C for this type of work, but any language that supports file I/O on a byte level will work.
Third. You will need to open up and take a good hard look at the world save files with a hex editor. Then compare this information with the arrangement of the blocks on the world. Start recording every pattern you see, you'll start to see that there is a pattern between the way the bytes are ordered to the formation of the world.
Then you just need to start changing things, write a small program that will find any instance of 'Dirt' in the world file and change it to the instance of 'Diamond', It will be a pretty easy program to write in C once you find out how the blocks are arranged.
Then you just continue your journey, write an algorithm to generate a map, you'll be able to do whatever you want the world file now.