I trying to do the same thing on my 620. Planned on taking all winter to rebuild her - and now I'm in a rush to get her put back together. Here's how it looked a few weeks ago:
Now, I've taken the back wheel off to replace the back tire.
I did the water pump on mine while it was apart. I found that I had much better luck putting the new seal in with my thumbs. I tried using a press, and it just distorted it.