Nope they are reusable.
Glow plugs are real easy to do...
Remove intake system all the way up to the turbo (Includes CCV)
Unbolt the main engine harness plug (drivers valve cover)
Remove intercooler tubes
Move heater hoses towards the passenger side.. of passenger valve cover
Unbolt valve covers (need a wobbly for a couple of the rear ones and the ones next to the AC box)
Using needlenose pliers pull out the plugs for the glow plugs
Break the glow plugs loose with a 1/4" drive deep socket(other sizes can get hung up on rocker arms)
Then get a 3/8" section of heater hose and push it down over the end of the glowplug, use it to spin it all the way out of the motor (this works excellent to install them as well)
Then stick the new one back in... same procedure for the rest of them...
Zip everything back up and your ready to go...