If you're running to lose weight, then min/max, or interval training, is the best way to go. 5k is a lot to jump into right from the start. Here's what I did:
First, start by eating regular, small meals. For breakfast I would have a bowl of bran cereal with skim milk. Lunch, a grilled chicken salad, or something else with a balance of protein and fiber. Then, later in the day, a small bowl of oatmeal. If I get hungry in the middle, some raw almonds are really good for you. Omega-3s and all.
Second, cut out as much sugar as you can. Eating fat doesn't make you fat, but eating sugar does. The biggest culprits are drinks. Water, coffee, and red bull total zero are about all I drink now.
Third, start out walking. I started with 2 miles a day, walking, for a week.
Fourth, when you begin running, do intervals. Warm up walking for 10 minutes. Then run as fast as you can for a minute. Then walk for a minute. Alternate these two things. Over time, increase the amount of running that you do in between walking segments. I now do 2.5 - 3 miles a day of interval running.
Fifth, get stronger. Do some lifting, too. This helps your body turn the food that you eat into muscle instead of fat. DO NOT LIFT EVERY DAY. This is a common mistake, but all you end up doing is tearing down muscle without giving it a chance to grow. I lift every 2 - 3 days.
Sixth, sleep regularly. In combination with everything else, sleep burns fat, but only if you get enough.
Seventh, don't give up. Results come slowly, but they do come. There have been a few times where I've said, "Fuck this, its not working." But then people tell me that I look like I'm losing weight, and I see pictures of the change over time. It does work. Its just not an instant thing.