Is it advisable to talk about "learning things I don't know in the field" as one of the plans for future in statement of intent?
Although I don't want to say what you should or should not write, this is my suggestion.

There is a difference between a Masters by Coursework and Masters by Research, as in the latter you most likely will be asked to provide a new contribution to science, while for the former you will most likely 'simply' extend your knowledge through subjects.

Knowing it's an application for Masters by Research, I suggest reading up on the research you're interested in, mention why you're interested in it and how you can contribute to that field. I think the reviewers are more interested in your enthusiasm and how you can contribute.

Mentioning that you're willing to take credits is a sign that you're afraid of not knowing enough, and could be a sign for reviewers that you're not confident. On the other hand, it does show that you know your limitations - but when you decide to mention it, don't make it the main item of your letter.

In the research field however the learning does not always happen through subjects, it most often occurs through literature review. Although subjects are very beneficial if exactly in the area of research, I think that it's sufficient to demonstrate that you are capable of working in the field of study.