[Questions about changing my username]

I am interested in changing my username, but I have some questions before I commit to doing this:
I guess I have a newer username, since I don't see any "." in my name, so I assume my last name is "Resident", is that right?
I never see the "Resident" part of my username when I am in SL or in my web account, so is the default "Resident" last name suppressed from display in SL?
If I change my username, I don't mind keeping the "Resident" part of my username.  It's better than the other name choices which appear in the last name selection options.  If I change the other (first) part of my username, will I have to change the (last part) the "Resident" part, too?
If I can keep the "Resident" part, and change just the first part of my username, can the new first part of my username have a "." (period character) in the new first part?
Thank you so much in advance for answering my questions!