What would I tell you?
Hhhuuummm... 1st train for sprints, then work your way up from there.
As for your knee, I would really suggest you seeing a Dr. and making sure it's OK to start a full on training plan. Just a check out before starting down this crazy road, wouldn't help.
After the Dr. make sure you get some GOOD SHOES that are made for your stride/form/strike. Good running shoes are worth the money and money saved on Dr. bills because of injury.
Finally... I will tell you... you can do it. GOOD LUCK!!!!
"Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather, to skid in broadside thoroughly used-up, totally worn out, and loudly proclaiming: WOW WHAT A RIDE!!!!"