Naturalized citizen here: it's not hard at all. You've had the green card for 10 years so the marriage is not even a consideration. For once, you'll be on the "friendly" side of USCIS that wants you to succeed, not the one that wants an excuse to deny.
If there are no issues (that is, no criminal record and no extended absences), then it's a simple and straightforward process and we advise all our clients to handle on their applications on their own and save themselves the legal fees.