Will it be hard to learn both Chinese and Japanese at the same time?

I am born in china so I already know how to speak chinese fluently. I just need to learn how to write. I'm currently going to take Chinese 101 in college and I was thinking about taking Japanese aswell my second semester.

I heard that the hardest part of learning Chinese is pronunciation (easy part for me) and the hardest part of learning Japanese is grammar.

I'm pretty devoted to learning both languages. Do you think its possible to learn both languages at once under my circumstances?

How effective is the language learning rosetta stone for Mandarin?

I'm not interested in writing or being able to read Chinese, I just want to be able to speak and communicate with people.

The idea of learning a language in a class room environment is torture to me.

My plan is to use the Rosetta Stone for my first semester and study abroad in China during my second semester. I hope that by using the Rosetta Stone I can have a fairly good understanding of the language and when I finally get to China, my Mandarin could only improve even more.