The first thing to do is to start working on speed. Here's a simple workout for that. Find a grass field where you can sprint for maybe 100m. I suggest grass over a track to keep you from worrying about times.
Run easily to warmup until you feel ready to run fast. Then do 8-10 x "100m"; actually 15-20 seconds will suffice. You want to start off moderately fast, and accelerate as you feel. You should get faster over the first few repeats. You can work up to sprinting, but think of that as something to develop over several weeks.
This is about practicing running fast, not sucking wind. Between repeats, take all the recovery you want. I suggest slowing to a walk, then think a bit about how you were running and what to work on for the next repeat (leg turnover, arm carriage, knee lift, extension, etc). Then start jogging into the next repeat.
Do this once a week. You may see some immediate carryover to your running. It would also be good if you got a pair of racing flats or such for this workout. If you find the right bit of grass, barefoot would be even better when it's warm; it's good for your lower legs, and it feels real primal.
The second workout to start doing every week is some sort of progression run. There are lots of ways to organize such a run; I suggest you go simple. Start out very slowly. As you warm up, gradually pick up the pace. Keep doing this the entire run. You're looking to run more or less as fast as you can while staying relaxed. Toward the end, it may require some concentration to keep rolling. You can do this more than once a week as you get the hang of it.
Read this thread.
http://www.letsrun.com/forum/flat_read.php?thread=3422852In particular, read carefully every post by 'malmo'.
And, if possible, get your long run in over a hilly course.
There are lot of things you can do, but this is more than enough to get you started for six weeks or so.