Hey...I'm new here, and I swear I've tried to search the forums for info before asking

but I'm not coming up with the info I need.
I want to spend less than $10K, and I'm looking at 300 Diesels (I've read enough about the 350s to stay away!).
What are the pros and cons associated with the 5 and 6 cylinder engines?
Instinct steers me away from odd numbers of cylinders.
How about turbo pros and cons?
Also, one of the reasons I'm looking at MB is safety, and I need headrests in the back seats...I think I start seeing them around '86.
Any help/suggestions would be greatly appreciated.
Peace
Charlie