Carlton,
It sounds like your motivation is there, now it's just time to act on it. Just some thoughts that I hope will help...
Don't think of the big picture with this one, just take it one step at a time (literally) and one day at a time. Start out doing something every day that you are proud of and then build on it. It can be big or small. Like if you have a particular weakness for a certain food, give it up for one day. Take a walk around the block one day. Then take a walk AND give up your favorite food one day. Then make the walk a jog. Then make the jog a faster run. Then increase the distance. Take it slowly and focus on the positive.
If you think you are eating bad stuff, try substitution before abstinence. Like, if you eat regular potato chips, go for a baked chip and then for a smaller bag of a baked chip and eventually no chips at all.
Don't go all or nothing. If you backslide one day, don't think of it as condemnation on your whole effort. Just give yourself permission to not be perfect and start the next day again.
Choose a goal race to work towards. Keep the goal modest but real. If you're worried about your time, pick an untimed fun run or a trail race, just something you would feel good about accomplishing.
You can do whatever you set out to do. Just stay focused and think positive. Good luck!