Breast feeding moms- weaning at 12 months?

So, I know we are still 4 months away, but I'm stressed thinking about weaning my baby at 12 months. She's ebf and I would like to start weaning around a year. I know it needs to be done gradually, but I'm just not sure how to start and how long it takes to fully wean. I'd like her to be completely off the boob by 18 months. Are middle of the night feedings the last to go? Do I start by replacing a day time feeding with a bottle and slowly add more bottles over time? Any info is appreciated!