You are not alone - this freaked me out, too! We had the perfect schedule and I was so worried to tweak it. Fortunately, kids are way more resilient than what we give them credit for, so chances are they'll roll with the punches just fine.
At mealtimes, give both a bottle of formula and a sippy cup of milk. They may not touch the sippy cups but that's okay - they're simply getting used to the idea. I decided to go cold turkey at 12 months (well, once we ran out of formula which was at like 12 months and 3 days...). I panicked and thought there was no way he'd go for it. Much to my surprise, he took to the sippy cup like it was the normal routine he'd been following all along. My point? Don't be scared to switch because they might do just fine.
At sleep time, I switched up the routine slightly. My son didn't get a bottle before nap but he had been getting one before bed. Instead of getting the bottle for soothing, we added a new book to the routine and then put him down as usual. Again, I was so worried he wouldn't know what to do but because the routine was so similar, he just went to bed without problems.
Good luck to you!