It won't be any more difficult than going from deficit to maintenance when you are not pregnant. First trimester you would eat normal maintenance calories (as if you were not pregnant) so it will be the same anyway. Just use those first few months to get to grips with maintenance and then when second trimester sets in, you will be a bit more prepared to up the calories a little (although if you are still really overweight you could maintain the same calorie level until the third trimester)

I googled how many calories I should eat. Your baby will be fine if you eat at a deficit - you're not going to be starving! Women in third world countries manage to give birth to healthy babies.

I'd say eat what you're comfortable eating, and eat more if you're hungry. I was nauseous until week 14 so I ate more carbs because that's all I could stand. Towards the end I got hungrier, but I exercised a lot, and I worked, and had 2 children already to run round after.

I exercised in my first and third pregnancies and was more careful about what I ate than in my second pregnancy, but I gained about the same in all three.

Your doctor can also tell you what your expected gain should be. Play around with your maintenance calories and see how much you are gaining. You really should gain anything until second trimester.