Sounds like all is well, but a few things that have helped me out in the past for future reference.
1. While I can't speak to second owner situations, when I was servicing tanks I had Ecotech replace M1/L1 pump bodies, drivers, and power supplies well out of warranty if it wasn't a case of customer abuse.
2. I used to clean return pumps by just running them in a bucket of warm citric acid and then scrubbing the parts off with a toothbrush but I found that this didn't always get the calcium buildup out of the rear impeller bearing. Now I take the impeller out, sit the pump with that opening upright, put in a teaspoon of citric acid powder, and a bit of hot water. Once that's done doing its thing I go through my usual steps, reassemble and run it in the bucket, followed by some time in fresh water to rinse everything out. Not that I need to clean pumps often, but this has reduced the frequency I have to clean them at.