My wife and I tent camp virtually every year in Acadia and I'd like to offer a few bits of info you can follow up on.
There are two camping areas run by Acadia: Blackwoods and Seawall. Blackwoods requires reservations. Seawall acts as an overflow but it's nice but much further down the road. For a car camping site you can use any of the non-electric sites. I always recommend anything between A-14 and A-28 because it's on the outer loop along the ocean and there's a "secret path" you can walk through which will take you right out to the ocean where there's a bench and you're about 50' above the crashing waves and gorgeous Maine coastline. You can buy wood at the grounds or you might want to buy some on the way in, especially hardwood.
You don't need a car there. There is now plenty of transportation via bus everywhere on the island. You can also begin hikes right from Blackwoods up to Cadillac Mountain if you wish. It's a nice, long hike that shows off a lot of the pretty views available there especially at the top. You can also take it into Bar Harbor where you can't swing a dead fish without hitting some excellent eatery. Plenty of selections to choose from and the prices aren't too bad, either. There's a Hanover Grocery store in town should you want to do your own cooking. Also plenty of breakfast joints there.
Showers are NOT on the campground grounds but just off the park. You'll drive right past them as you begin your turn into the park. Take quarters. Very very clean, open, well lit place, believe me.
If you want one really challenging hike, do the "Beehive". There are plenty of spots of literally hand over hand vertical climbing if you have the stomach for it. There are plenty others, too, like the Bubble Mountain hike which is more scenic for older goats like us.
Finally, I'll put a word into this answer about Jordan Pond. If you have the time, eat a lunch there, on the green on a picnic table. Order the traditional lemonaid that you sweeten yourself along with just outrageous popovers. It's a bit on the pricey side but if you want to experience something from the late 1800s, that's the place and the view is excellent. too. There's a totally flat hike around Jordan Pond in front of you that's quite long.
If you have any other specific questions feel free to email me directly and I'll be happy to answer if I can. There are plenty of brochures and books out there about what Acadia has to offer.
One last thing; you MUST.....and I mean MUST watch this video on YouTube: https://www.youtube.com/watch?v=T9teAdBu89k It's called "Acadia Always". Please watch it and you'll begin to feel the magic of one of the most visited national parks in the country.
Rome (CT resident for now, Maine in the near future)