Writing a master thesis in a totally new field?
It might be different from country to country, but where I did my Masters project (Denmark) your judged on what is expected to be learned (with of course a basic-level start knowledge) within the allocated time for the project. Hence, I would not advise to take a year out to get acquainted. 

However, it should also be noted that in Denmark you get money to study and so a year of would mean you would need another income. Opposite to other places (like US) where it cost you money to study.