Haven't done any competitions, but we did quite a lot of obedience training with Maggie the Puppy Pie and she is now an AKC Canine Good Citizen (prereq for most animal therapy programs if you're interested in that). You'll soon find out that obedience training is more about training the owner than training the dog.
Even if you go nowhere on the competition circuit, you'll have a wonderful time pursuing it, so just go have fun!