Id have to disagree with your assment of incompetent bmw mechanics around the place. From what ive read in this forum alone the quality of bmw knowledge is mind boggling, if the folk posting here are a representation of the bmw community in NZ we're pretty safe in getting guided in the right direction.
As a professional outfit specialising in bmw I reckon Auckland is a pretty small place to hide and try bluff your way through. Theres botany motor works in south auckland, bm workshop in central auckland, and bell bm in silverdale. I havent used any of them but their reputation far preceeds them. Thats auckland pretty much covered.
Then you have folk like andy who can stuff a V12 into a little hole and have it running and maintain it and likely hes seen everything. Brent at bmworld whos done similar and knows probably exactly where every bolt and part came from by looking at a grainy cellphone pic. And probably 20+ others with practically infinate knowledge.
e38.org is best bet for everything e38. Ive read the hell out of that site and I dont even own one of those cars. Ive read about edc delete in step by step detail, part codes and the functionality of the result in detailed review from google search. Its all out there and freely available.
Clipping the ticket is part and parcel of doing business and providing a service. I do it, thats how people survive. You're not forced to buy and likely you're fine to provide your own parts and pay labour alone.
You read like you carry this giant chip around on your shoulder like a full grown siamese twin robbing your blood and ingested nutrition. Thats just how I read it though. The very first reply outlined what you needed to know and the subsequent answers practically pointed you to exactly what you needed to know and you seemingly choose to blow them off because they didn't suit you.
I come here seeking the knowledge these folk have too, Im aware I should be polite and courteous of them taking the time to respond and gift their knowledge and advice because I know if im not, itll be remembered and they wont bother in future.. but thats just how I see it.