Thanks for the info, alliemac! Very helpful to know that I won't explode the water system when I inevitably overfill it, and how you deal with it generally. Seems like an over-complicated and inconvenient system ...
I'll let you know about the antifreeze pump function--I think that the previous owners used it, as they gave me a short hose that they said they used (about 4 feet of plastic tubing with a hose attachment at one end). I'm planning on sanitizing the water system next week (it's in the shop now having a broken brake line fixed) so I'll report back on my results. My owner's manual says that when using the "winterize" function on the water panel, it does not put antifreeze into the fresh water tank.
How do you winterize your water system if you don't use antifreeze connection?