With regards to your 5K times: don't train like you are racing, train so that you can race. Another way to put it is, regardless of the distance that you are running, make sure that you can run the distance. Do your speed work (as in intervals once a week), and you if you have the right stuff, you will naturally see your everyday times get a little better every week or so. The point is that as your endurance levels improve, so will your ability to naturally run faster. It will happen without you really realizing it. Then on race day you will reap the benefit from all the training and you will be surprized at how well you can run.
But while you are training, if you want to see how fast you can do a 5K distance, find a 5K event some weekend and run it as part of your training program. The cool part about doing that is that if, for example that day is supposed to be an 8 mile day, run 2 miles before the event, run the event, and then run another 3 miles afterwards - tadaaa... 8 miles and an awesome workout.
Have fun,
-bill
http://runningthrutime.blogspot.com
(what do I know...? I'm just getting old...)