I dropped it and now it will not fire. How can I diagnose the problem myself? And, once I have figured that out, how can I learn to fix it?
A camera is a precision mechanical device with a lot of very accurately built moving parts. I'm afraid to say that, if you're asking for advice on how to diagnose the problem on the internet, then you don't have the skill needed to repair a camera. This isn't like fixing a car - it's more like repairing a Swiss watch.
By all means, try to learn - but if you value shooting with this particular camera and are not okay with the risk of absolutely destroying it, then it's best to send it to a certified Pentax repair shop.
RE: general diagnosis - you would want to check if the film advance lever was able to load the mechanism. When you fire a shot, does it feel like anything is happening? Do you get different results with other shutter speeds? Is there damage to any other component? Does your lens stop down using DoF Preview?
Again, it'd be good to do this so that you can get a feel for the overall damage. But, you should write up your findings and send the camera in to the shop.