I recently replaced all 6 glow plugs and their controller on our 2009 x5 35d. See my thread for details. ECS Tuning sells a kit that includes the 6 glow plugs (Bosch) controller (Beru) and all the intake manifold gaskets for $312.44.

I followed the great post on how to remove and replace the intake manifold by sgrice

Don’t even think about just replacing one glow plug. The majority of the labor is getting to the glow plugs. The small incremental labor/cost of replacing all 6 and the controller is a no brainer.

Funf Dreisig