Ha! Way to go Bob! The windshield advice is the best and one that most
would overlook. Moisture gets into those windshield chips and, when
the temp dips to freezing, the windshield cracks. Have these things
repaired ASAP, even if not approaching winter.
Sure, the 50/50 ratio, as you would do for any vehicle.
As far as the fresh water plumbing, I have always just opened the
drains, left them open, and that is all, with no adverse results, down
to -30F. I kind of like the idea of having a fresh cocktail waiting
for me, though, so I give high marks to the alcohol suggestion.
5/50 Castrol Syntec is what I've used for the above mentioned temps.
Don't forget to put some of those Dcon mouse bait wedges in
there....don't know how bad the mouse problem is in Bend, but here in
Colorado, at my 9000' elevation, if you don't take precautions, they
move in.....with horrible results!

Gracias,
 Miguel