I suggest you either remove the T-stat housing and use a spray bottle sprayer to empty it of coolant or disconnect the lower radiator hose and run the car for as long as it takes to drain the coolant.
Reason for this:
To prevent leaking coolant into the engine when removing the lower intake manifold.
Seems this has been a growing problem the past few years when replacing the LIM gaskets, causing the bearings to sieze up.
Also, drain oil and leave drain plug out so if any coolant does get into the lower end it hopefully will just drain out. There will still be some coolant drops in the engine so, put oil back in upon reassembly of the upper end, and run the engine for no more than 2-3 minutes at idle. Then drain oil as well as replace filter.
Check oil before draining to verify upper intake reinstallation was done properly and no more coolant got into the engine/onto the block (with external engine visual inspection).
A little bit of a mental burden initially, but it could be a mental stress relief, as well as monetary insurance when you find your engine is good for another 100K+ miles.
Also, when refilling the coolant, save some money and get the regular green Prestone or the Prestone that is compatible with Dex-cool.