Show different theme for admin?

I’d like to test some theme changes on my live site, but I obviously don’t want regular users seeing any errors that may arise from it. I’d like to just duplicate my theme folder and if I’m logged in as admin, then that theme is shown to me, otherwise, the old theme is shown to my users.

Change “Enter Title Here” help text on a custom post type

I have a custom post type created for a directory that will end up being sorted alphabetically. I will be sorting the posts in alphabetical order by title, so I want to make sure that the Title is entered as last name/first name. Is there a way to change that default help text — “Enter Title Here” — in my custom post to something else?