Thanks to all who responded. I have now found the main drain valve, which is under the bed and has a large yellow handle. It is SO obvious that, until today, I hadn’t realized it was a valve at all if that makes any sense.
I knew my Chalet was a prior rental but am not thrilled to learn that it was sold only to rental companies; I’m sure “rental grade trim” is inferior to what retail customers get. Oh well - perhaps I should have known better, but too late to worry about it now.
As to the mirror, I have ordered one that can be screwed to the existing mirror frame or, I hope, to the supporting horizontal bar. If that doesn’t work I am off to Wal-Mart!
As is likely obvious I, though somewhat long in the tooth, am a new RVer. I see how these forums, in addition to being good sources of information, can be a lot of fun. Hope I can contribute something useful one of these days.