[Andreas]

I'd do the following:

1) Make sure both run the same version
2) Shut down the live board
3) Make a backup of all files and the database (just in case anything goes wrong)
4) Upload all files form your test board
5) Export style & language from your testbord
6) Import both at your live board
7) If you made changes to the database structue do the same changes to the live system
8) Check if everything is ok
9) Open the live board