Mine probably would have been about 4 hours but I had severe gasket surface pitting so I had a detour to address that issue.

George

 

I took my time when I did it on my own taking a weekend.

 

I had water leaking out from the seal on the front of the intake manifold. I took it to RMS Auto shop in Houston, and the front office estimated 4 hours. Later I got a call. The mechanic was claiming the manifold itself was corroded and could not be repaired...and there were no new ones available So I was out of luck.

I bought one on eBay and took it, and a complete gasket set, back to RMS and told them to replace the gasket. Another call. The mechanic was complaining that the old gasket was in pieces and wanted an extra $200 to clean it up before installing the new one. Fine I said just give me the old intake manifold when I come to pick up the car.

Long story short, the original intake manifold was completely undamaged. The mechanic just didn't want to do the job for 4 hours labor.