Plan to change the oil separator, how much is it

[bulkwarrior]

I'm contemplating about changing my 06 E53 4.4i's oil separator. After reading a lot of information on this forum, I suspect the misfiring and shaking during a cold start in the morning might be due to a faulty oil separator. This problem only occurs when I park the car outside and when the ambient temp drops to near 32. I would like some input on where to have the job done.

Is it a very complicated or BMW X5 specific job that must be done by the dealer? I think the dealer will probably charge about $1500 for the job, while some other reputable shop in my neighborhood might only charge a few hundred. Had anybody had the job done by a non-bmw repairshop? How much do they charge for the job(including the material)?

thanks.