There's several scenarios and nobody can predict how exactly it will go.
1) You can have I-751 decided before your N-400 interview and removal of conditions interview will never be conducted
2) They may do I-751 interview on same or different date to N-400 interview
3) You can have N-400 interview only and they'll tell you they can't decide on N-400 because of pending I-751, then will decide I-751 few weeks / days / months later with or without additional interview
4) They may conduct both interviews and give you decision same day with oath on same or different day
5) They would typically start N-400 interview with civics test followed by yes / no questions, or do it the other way round.
Either way, because you're applying based on marriage to US citizen, I highly recommend taking the US citizen to all interviews you're scheduled for.