Do I need to book an appointment and what are the requirements for a 1 year marriage extension in Thailand?

Going to apply for a 1 year extension based on marriage. A few questions.

1) Do I need to book an appointment (in Chiang Mai)?

2) Is health insurance needed for extension based on marriage? Is there an up to date list of what is required? E.g. photos at house, hand-drawn map.

3) The 2 month mark for the 400,000 being in my bank will be a day before my visa expires. Is there any flexibility in the 2 month limit, since I'd prefer to deal with all of this before the last minute? I'm assuming not, but thought I'd check to see.