Thanks for your input Joe.
It's really hard to tell where the leak is coming from. The bottom of the oil filter (which was replaced) has a few drops of oil on it. The bottom of the transmission pan (automatic) is wet, and the frame cross member that supports the transmission is wet with oil. The "puddle" is directly under the cross member.
Part of this work was to replace both valve cover gaskets. During inspection of the area it was revealed that the intake manifold gasket had developed a minor coolant leak so the intake manifold was R&R with a new gasket; while performing this work one of the bolts broke off and was R&R. I can't see any oil around the base of the valve cover gaskets.
This was not my local Chevrolet Dealer; if this had been something other than "just" a radiator problem I would have taken it to them; it morphed into the extended problem. Mieneke Auto Care Center
has worked on my truck in the past with excellent results; this time they appear to have blown it, just not literally, I hope.
But regardless of the company that did the work, the shop manager should have done a road test and approved the work before it was let out of the shop.
We'll see how it goes.... in the meantime, I am again back on two-wheels to get to work.