you have time........
just do something like this:
http://www.halhigdon.com/marathon/inter1.html
They say if you just stick to the long runs and can do them, you will be fine.
As for speed, this is just my opinion, but if you can do some HIIT and sprint work, it will will really get your mile pace down (im american and refuse to convert my thinking to metric b/c it makes me has a confusion)