I did my headgasket on my M3.
It took a week (including 5 days waiting for the head to get back from the machine shop)
Car started on 1st crank. It had a check engine light due to a vacuum leak. It was a hose I had left unconnected. The CEL went away by itself and I recovered probably 30whp between the previously mistimed engine and leaky HG both fixed
Where are ArchDuke and Logansteno? They are peons when it comes to E36s compared to me