Two most important questions:
1) How much weight did you gain?
2) What sort of non-running exercise have you done (hiking, flag football, softball, etc.)?
I have pretty good natural footspeed too, and I also ran pretty low mileage in high school.
Because I play sports in my free time and haven't put on any weight, whenever I feel like running again it usually only takes about 6 months of dedicated training for me to get back to where I once was.
Setting new pr's is then the tough part and I usually lose interest because I don't have anyone to train with.
But as long as you aren't a fatass, I say a year will get you in damn fine shape.