I Want to Become Mandarin FLUENT (Beijing)

Hi,

I will be staying in Beijing for a little while. I love China and I want to learn mandarin very badly but I need a school-type of environment to learn it.

I probably would go to another city like Xi'an or somewhere cheaper than Beijing but I'm wondering a few things:

- I'm on 1 year 60-day per entry L visa. If/when I decided to actually commit to a school, is it possible to change visa types so I don't have to keep leaving? Are there some kind of requirements to do so or can I magically change into a student visa?
- Approximately how much does school (only Mandarin) cost in China for a foreigner?
- How LONG do you think it would take to become fluent in Mandarin, including reading and writing?