I just changed impellers and housings which is not one of my favorite jobs. I stumbled onto something that might make getting the impeller into the plastic housing easier for you. I put the impeller on my bench and slipped a hose clamp around it and snugged it up. I positioned the vanes in the correct direction with a needle nose as I continued to tighten the hose clamp. A little dish detergent on the inside of the housing before inserting the impeller and removing the clamp. Kinda like a piston ring compressor to install pistons. Tidied things up with the needle nose and was done. For what it's worth...Lou

That's how I did my first one. AudioFn showed me how to do my second. Grease up the impeller, put the housing in your left hand, the impeller in your right, align the two and push together while twisting with your hand. The two slipped right together. I've changed a couple of them on the water with this technique and it works pretty well. And don't worry about the direction of the vanes. They'll flip around on their own.