Hello and congrats on setting a new goal. I finished my first HM last year and used forums like this and my father (he's an ultra marathoner) for advice.
A HM would double the distance you can walk easily. It's doable and the first thing I want to point out, you can walk many HM races. Definitely figure out what the timeline is to ensure that 13:45 pace you were talking about.
Do you plan on running it, walking it or a combination of the two? If you plan on running part of it, how is your running? Are you new to running or do you have any type of base? Other big item, train like you are going to execute your race. This includes clothing and accessories. Try and run in what you will run in during the May timeframe and if you are going to use water belts use them during this training period. Lastly, it's your first HM and you've chosen to become part of an elite club. Plenty of people aren't even willing to walk 6 miles at one time in life. Congrats on that. You've already won and based of that, I would recommend your goal be to finish your first race injury free and if that means walk it then walk it. Don't worry about PRs. That's for your follow on's if you decide you like this journey.
Easiest thing is to get a trainging plan and there are several out there: Hal Higdon, McMillian, Jeff Galloway. All will give you plenty of informaiton so browse their sights and find one that works for you. I'm blending a couple of people. Hal Higdon's 12 week plan (3-4 days running tops and it doesn't go over 10 miles), with Jeff Galloway's run/walk for the long runs which I use as an interval element to my training and I even have some other speed workouts from McMilian Running. Is there any groups around the area you can join or would want to join? Like I said, lots of stuff.
As for January, continue to do what you do. I would recommend a 3 miles run base (if you plan on running it). In the Navy, when we train and run on a treadmill we utilize a 1.0 incline not a 1.5. We've even run marathons on them while deployed so don't feel like 1.5 is the magical number.
Biggest thing is to get the routine of working out (cardio, strength) and time blocks set in your schedule during January. The rest of the timeframe will go by very quickly.
Good luck and let us know how your journey is going!
SEP12: Rock N Roll HM: 3:04:04
| current weight: 150.2