I'm no expert, there are plenty of people who know more about this app than I do. However, I have been able to 'teach' my wife...
1. ...as I understand it, a new, complex password will be created in place of the ones I'm currently using.Nope. It can be used with that sites "Change/Edit/etc." password that any good site would have. But you will have to do the 'old password' entry manually. Of course, you could also just create a set of passwords you already have (from memory or however you have them 'secured' someplace, even KeyChain). You could then log in with the old p/w with 1Password and then use the app when you use the 'change/edit/etc.' function on the site.
2. [Some] sites have very specific rules about passwords [...]. How does 1Password match its' password to these rules? It doesn't even try! A
good site will tell you what its p/w rules are, if there are any. A
poor will let you know what 'rule' you have violated. A
terrible will simply clear all the fields and make you
guess what the rules are!!! If there are rules/limits, you can adjust a couple of sliders in the 1Password password generator. Otherwise, I usually select at least 14 characters to include upper & lowercase letters, digits, symbols (*, %, $, @, etc.)., avoid 'ambiguity', and dis/allow repeats. There is a "Recipe" to set all this up in the password generator.
3a. Would I disable Keychain in favor of 1Password?No need to, it actually stores some things besides passwords, anyway.
3b. f it is disabled, it seems that it will be hard for me to remember my dozens of existing logins.That's rather the main point of 1PW; not having to remember
any site's password. 1PW does this for you! When you hit the 'Login' page, you simply click the 1PW menu icon and 1PW will offer all passwords saved for that url (sometimes a site may require different login info for different areas). You then either tap 'return' of scroll to the desired choice and hit 'return'! At no time is your password ever visible... unless you specifically want to see it, of course.
4. Suppose I am away from home & create a 1Password login [...] wife (back at home) [...] how would she know that the 1Password login exists?Sounds like you'll be creating a shared group of passwords (for you & your wife), to be used on multiple computers/mobile devices. 1PW can sync between various machines, anything that can run the app, so all machines will always be using the same collections of passwords. DropBox might be the best way to do this for you, since you may in two completely different parts of the world. Otherwise, you can use WiFi or your local network.
There is one thing that may trip you up in this shared password collection;
how will the second person know there is a new p/w? You could text/email/phone(!) the other person and tell them a
new p/w has been created for a site.
NOTE: You do
not tell them what the password actually is. Assuming you are syncing things, all the other person needs to know is that there is new info stored for that site. Even if you don't tell the other(s), part of what 1PW stores is the URL for the site, so, if either of you don't have time to tell the other about a new site, just do a search in 1PW and it should pop up! This, of course, assumes it has had a few seconds to update/sync with the 'master' list. I would highly recommend you let your wife know about any site
you where you create a p/w!