rebal

HEY guys ,I have a good friend in Los Angela's area (San Fernando Valley) who needs a a real good Diesel tech for his duramax powered Kodiak 4500.do any of you know of a REAL GOOD shop down in Socal? A # would be great too if possible. he has 100k on his and it developed a knock ,I think it might be a Injecter . He said its always had good PM and was not low on oil.the shop its in now wants to sell him a engine from one of his trucks and claims his duramax in his pick up is a larger motor then the one in the kodiak...hummm both are 6.6L hows that work? and that he will rebuild my friends and reinstall it in his truck when done. something sounds fishy all for around $8000 .
if anyone has a name for a honest shop could you let me know
Thanks guys
R