I've been running for most of my life - I most enjoy the ten-mile and the half marathon, although I also do 5Ks, 8Ks, 10Ks and triathlons. Definitely start with the smaller distances and work your way up - most marathon training plans I've seen recommend a solid year of running shorter distances, plus an 18-week marathon training plan.
Starting out with a plan...my non-runner husband did the Couch to 5K thing earlier this year and liked it. I use Hal Higdon's intermediate and advanced plans for training, but his novice plans I've heard are great. I also have beginner friends who like Jeff Galloway's plans.
Congratulations on joining the running world.
I admire you - I will probably wait until later in life to try a marathon because I currently work 60+ hours a week and only really have time to train for shorter distances. PM me if you ever need help.