This is easily done and it should be part of your annual maintenance
routine - as I am sure now it will become. All you need to do is gently remove the face plate to the water
pump on the engine and then gently remove the impeller. I find the bent needle nose pliers (the ones with the 90 degree bend) to be the easiest for the job. Don't worry about thrashing the impeller pulling it out as you will replace it with a new one. Be sure you don't score the inside of the pump, either.
Examine the impeller. Likely as not judging from your question it won't all be there. Some of it has broken off and lodged itself in your heat exchanger
. You may have to pull that off and clean out all the rubber bits. I have in the past found impeller bits lodged in the 90 elbow
coming out of the pump that never, fortunately, made it to the heat exchanger
I use a little vaseline on the new impeller to get it rotated into the pump. It does not matter which way you bend the blades (despite what you may hear) as when you first start the engine it will spin it into the proper position.
The face plate may leak. This may because you forgot the gasket
. Some pumps have them (usually made of paper) and some don't. Examine your faceplate carefully. If it does not have a gasket
DON'T put one in. The gasket usually comes in the impeller package.
This is an easy job. Get used to doing it and you will feel some satisfaction in an ever deeper relationship with your engine.