The best way is probably minetweaker (or crafttweaker in 1.10, but that's just a renamed minetweaker). They have plenty of documentation on their wiki to help you get started, en there are a lot of people on here willing to help if it doesn't work.
I'm not sure what you mean. If you want to change a recipe, just remove the old one. Minetweaker does not make any files that add the normal recipes, it just allows you to remove the normal recipes to replace them.