I finally got it working the way I want... and now I understand "indented block"
Here is the code if someone else (newbie like me) might want it.
from telnetlib import Telnet
if xbmcgui.Dialog().yesno('Power OFF Server','Are You Really Sure?'):
tn = Telnet("192.168.1.210", 3210)
dialog.ok("Power OFF Server","The server is shutting down...")
You'll need PowerOff 188.8.131.52 on the server. Just google it...