Originally Posted by ZetaTre

Not necessary: having direct injection it will fire up without the intake.

Just swap the glow plugs and fire up the engine. You will get all sorts of codes, but all you care about is the one for the glow plug.

When my dad's glow plugs were shot, the code came right back after a few minutes from startup

Erase all codes, fire up the engine (it will be loud if, particularly if you don't plug the EGR cooler) and see if the glow plug code comes back.