I am seeing coolant around the valve covers as well as wetness under the throttle body on the side of the engine (but the TB is NOT leaking!). So do I go ahead and replace the upper and lower intake gaskets? Do I need to replace the intake manifold? Thanks for any info as I will need to prepare myself to do this task.

Yup, it is time. That'* how mine was leaking.

Remove the UIM and LIM. Your UIM is likely fine, but closely inspect it for cracks, melted areas, etc.

More than likely, your gaskets are leaking due to age and mileage. We've only seen one L27 UIM fail...and even so, that was marginally a failure.

Get a Chilton'* manual and torque wrench...they'll be your best friends in doing a project such as this!

While the specs on the bolts say 10mm, you will find a 6 point 3/8" socket fits tighter and I find that torquing works better with the 3/8" because there is no bolt rounding or slip.