Yes, pinyin and the correct usage of tones are very important in mandarin language. In chinese mandarin, there are a lot of similar tones but different meanings.

Without first learning the Pinyin, in fact, does not preclude the doctrine of Mandarin, this is not the most critical aspects of learning Putonghua. If it is in the initially learned Mandarin and understanding of a certain number of Chinese characters, and then learning Pinyin, and the correct pronunciation and continue to improve, and the time and effort to learn significant savings. Hope that is helpful to you

In my opinion,it is necessary to master pinyin first for a foreigner if you want to make correct pronunciation and type Chinese characters.Also,it may be less confused learning characters of Mandarin if you have mastered pinyin. However,if you only want to understand native Mandarin speakers or remember Mandarin characters,maybe pinyin is not so important. By the way,my grandfather doesn't know how to spell pinyin,but he speaks good Mandarin.

remember that pinyin is just a stepping stone to help you understand the language. Once your chinese gets to a more advanced level you don't need to study or learn pinyin, but it is still the easiest way to write the pronounciation of characters and to type characters.

Apart from it simply being the easiest way to learn properly, another thing to consider is that (IMHO) the simplest way to type Chinese is to type in the pinyin. You use a thing called an Input Method Editor (IME). You type in the pinyin, and it translates it into the Character. Often all you need is the letters, and it guesses which one you meant. If it gets it wrong you can either use the tone number, or choose the right one.