Is there a set way to form nouns like 'running' or 'talking' from their respective verbs, or do they just have to be memorized?
Well, yes, there are several patterns, but neither they apply to all possible verbs, nor they preserve verb's "universal" meaning. For example, there is noun "беганье" (by the way it follows a very common pattern in Russian), but you can't use it in this particular case ("Running is difficult").
how would you say "It is difficult to run"? Would you use это?
That highly depends on context and stylistics. But remember that Russian "это" isn't essential part of syntax as English "it". So you rarely put it in the first place. More usual way of saying should be "Бегать - это трудно" or just "Бегать трудно".