I was wondering what would be the correct way to get to the cam shaft on my 16.5hp. Briggs, in order to remove it and replace it with another new cam shaft?

Well, remove the engine from the unit, purchase the new camshaft, oil main seal, and sump gasket. Drain all the oil. Remove the pto pulley, remove the sump cover, remove the camshaft, remove the main oil seal, then replace all the parts removed with new ones, and then after assembly, add fresh oil.

Okee Dokee, thank you. I'll give it a try. What is a sump cover?

The sump cover it the name for the bottom pan, kind of like the "oil pan".