First, you should wait until September 2010 to apply for citizenship.
Second, you can marry your girlfriend anytime but your GC can't help her until you are a citizen, so she must maintain her status during the waiting.
Third, don't file I-130 for her before you become a citizen because it takes much longer time - I am talking about years - for a GC holder to apply GC for his/her spouse. As a US citizen, it takes less than 6 months. The best option is to file I-130 and I-485 when you are a citizen.
Last but not least, you may need a co-sponsor because USCIS will look into 2010 income if you file GC application for your wife in 2011.
People, please feel free to correct me if I made any wrong statements.
Best of luck. Happy holidays.