Can I get married while N-400 is pending?

Antonio writes, "I have recently did the paperwork to naturalize and since I am so excited, I also want to propose to my girlfriend, so that within the next few months I can truly embark on my American dream.  I wonder, though, if getting married before I am approved will complicate anything."

Actually, regardless of the immigration status of your girlfriend/fiancee/spouse, your naturalization application is your own.  If you do get married any time before taking oath, you will need to update that information with the USCIS (the best time to provide that is during the interview) or if it happens between the interview and the oath (at the time of checking in for your oath ceremony).  If not, you need not mention your relationship or engagement at all, unless specifically asked (there is no reason that you will be asked unless it comes up somehow).