If your pronunciation is shaky, getting a full grasp of English sounds is very important.
You might be able to do it investing only time and energy on good books and websites.
If it is too hard, you better find a good teacher and invest the money to get it right.
If you don't get the hang of the phonetics, you will probably never be a good listener.
So it is critically important, and the whole task of mastering pronunciation is not that big.
In relation to the entire language, it is a small part - you can do it in a short time.
It will be more difficult if you're already in bad pronunciation habit but I'm sure you can do it.