Hello hello!
I've done 5k's, and Half marathons (stand alone and as part of a half-ironman distance triathlon), and I'm 25 days away from my first marathon (Belfast City).
Like you, I was never a runner. I *hated* it and it was my weakest leg in triathlons. So I decided to check out some books. The one that really worked for me was called Chi Running (
www.chirunning.com). It has some parts that are too new-age for me, but the general information on form is really, really helpful, especially to new runners. It turned me into a runner!
And the single most important thing is good shoes. Don't go to a big-box sports store, go to your local running shop. They'll analyze your feet and stride, and put you in the right shoes (support, or neutral, or motion control if you're in that tiny percentage of the population). The majority of running injuries are caused by running in the wrong shoes. Be prepared to spend at least $60, and more if you have a foot that needs a lot of correction (the top of the line support shoe costs around $115!). Think of it as an investment: yes you've spent $80 on a pair of running shoes, but how much would physiotherapy cost you per session?
And your strategy for stepping up is spot on. 5k will get you a good mileage base, and then you can step up to 10ks, and then half marathons (i absolutely love the half distance). The marathon is the big kahuna...it's a scary prospect because a lot can go wrong (dehydration, over-hydration, cramps, chaffing, lost toenails, etc.) Sound glamorous, right
? But it's thrilling...it's like being in the olympics, with the streets lined with people cheering, medals, etc. You get the same treatment and medals as the guy who finished 1st.
Good luck, happy running!