Realistically, I think because you may be limited in terms of time and you'll be communicating with people one-on-one I think you should concentrate on speaking the language rather than its written form.
Hiring a tutor is a great idea. You could also get a language program that emphasizes the spoken language with common phrases and vocabulary. You could also find some webcasts so you can try to pick things up listening to people speak it as Mandarin is a tonal language.
I speak some Japanese and am learning Cantonese and Mandarin. Chinese is much more difficult because it is a tonal language. I bought a whole set of tapes from someone in Hong Kong a few years ago and it's helped some, but I still have difficulty because I'm not used to the different tones. The basics, like
how are you? and
where is...? come in handy and maybe some colloquial expressions.
You might also want to brush up on Chinese customs and etiquette, such as using a chopstick to eat, don't face a tea spout to anyone because it is considered impolite to set the teapot down where the spout is facing towards someone, and there are meeting customs and traditions. One important one: Do not give lavish gifts because it may be seen as a bribe and especially don't give a clock as a gift because give you a clock sounds similar to "attending your funeral." I looked that one up just to be sure.
I admire you, too, for learning the language and really being proactive. I am part Chinese and only now am I learning the language.

My martial arts teacher speaks Mandarin and Cantonese so I am hoping to improve by speaking with him. Maybe you can find a Chinese society or group to help you out.
GL!
