W211_E320_CDI

I have a 2006 E320 CDI with about 314K miles on the clock. One of the injectors has is in the midst of "black death" where there's a coal-like substance forming around the injector. It's started to smoke a bit on hard acceleration and I can feel a loss of power. I was wondering if anyone on the forum had a shop they could recommend in the Seattle area to take care of it. Hopefully they can just replace the seal and not the entire injector.

Additionally, when replacing the glow plugs most of them came out easily except for the rear-most one. It felt like it was binding in the head and I didn't want to break it off in the head, so it was re-torqued per the specs. Ideally I would like to replace this one as well.

Thanks for your help!