Hi John,
That's may be safest for you. Remember backup, backup, backup, backup, backup . . . . . . . . .
You can just copy the database and files - change name of database and files to subdirectory (like test).
Then update the details in the config file for your "test" copy and it should work
Once you've played around and worked out what needs to happen or if you've changed any files you can merge/duplicate those changes across.
Alternatively, if nothing much has happened on the site (may be the case for you??) you can just move your "test" files into the "live" directory and it's already hooked up to the database you've been working in.
...... what ever works best for you in your situation and how active non-admin content on your site is.