First Marathon Preparation Guide

I'm running my first marathon and need comprehensive preparation guidance.

My background:
- Running experience: [years running]
- Longest distance completed: [miles]
- Current weekly mileage: [miles]
- Race date: [date]
- Target marathon: [race name]

Please help me with:
1. What to expect during training
2. Essential gear checklist
3. Nutrition planning (training and race day)
4. Mental preparation strategies
5. Race week protocols
6. Race day timeline and logistics
7. Pacing strategy for a first marathon
8. Common first-timer mistakes to avoid
9. What to do after crossing the finish line
10. Recovery plan for post-marathon