Hi everyone, when my wife petitioned me and I received my green card, she was still using her maiden name. As a surprise to me for my birthday last year, she changed her name and legally took on my family name. We will be sending in our I-751 next week. Will there be a problem since her name is different now from when we filed my AOS?

It shouldn't be. The two of you now have the same last name and it is a very common thing for the wife to take the husband's last name. Since this is an application for removal of conditions for permanent residency based upon marriage to a US citizen, they know that you two are married (VBG).