[Retroman1969]

All excellent questions! I'll ask the shop how they did it.
It's not really spilling coolant as far as I can tell, but it's squeaking small amounts of pressure and steam from around the cap, leaving dripping moisture all over the area of the deck lid that covers the service area. I can see and hear it when opening the trunk after a long highway run. I'll check the tightness of the screws around the pressure valve.
I've never had a car with a bad head gasket that didn't overheat and boil over as a result.
Hmmmm... I did top off the fluid a bit when switching out caps. It's so hard to read the gage on this new tank I could have filled it a bit too far even though I was trying not to.
Shop is doing a block pressure test in the morning so we'll see what that reveals as well.
Thank you so much for the input so far everyone!