I know I am digging this out of the grave but how did she get here? If she came here on some sort of a visa, then you dont have to complicate things with a lawyer.  The fact that you guys have been married for over 3 years is big plus, unless she was involved in crime and got convicted with a misdemeanor or worse. 
Follow the link below for a step-by-step, save your money:

http://www.visajourney.com/content/i130guide2