Hi L.,
I don't think switching to milk or formula and dropping breastfeeding need to be the same thing. I'm assuming that you started on pureed foods around 6 months or so. So your baby doesn't necessarily need to switch from breastmilk to formula, but can continue learning to eat more table foods. This part of it is something to discuss with your pediatrician. My daughter also wasn't drinking much milk when I tried adding Ovaltine (chocolately, but also has vitamins). My pediatrician recommended Carnation Instant Breakfast, but said Ovaltine was fine too. And yogurt is good too.
As for weaning, I dropped one feeding at a time, and it really worked great for us. I also breastfeed to 12-13 months. At that time I think we had 6am, 9am bottle (of bmilk at daycare, I pumped), 12pm bottle, 3pm bottle, 6pm. The first two feedings that got dropped were 10pm and 2am, when she slept through the night (wow, I already can't remember when, but I'm pretty sure it was well before she reached a year). She had started drinking less of her bottles at school, so I started by dropping the pumping sessions one per month. You may or may not have time to go this slowly. After dropping those, I dropped the bedtime feeding... this was very much a case of just not offering, and staying away from our "spot" at that time. We got in a bedtime routine (or strengthened it) of reading and rocking - so that she still got important cuddle time. For the final morning feeding, it took daddy getting her up in the morning and us relocating to the kitchen table instead of hanging out in our bed during coffee (darn, lost the coffee in bed!). Overall I had no problems physically, and she seemed to do really well with it too. Stopping slowly helped us hang onto that special time just that little bit longer, and I think we were both ready by the time we dropped the last one.