Coolant leak

Just finished replacing the head and intake gaskets on my 1997 and discovered a coolant leak at the passenger side base of the radiator where the round plastic disk rests into frame. Is this a freeze plug? And how difficult is it to replace?

Is this a freeze plug?
A freeze plug is a metal plug that presses into the engien block to take the expansion forces for freezing water in the event that water freezes inside the engine. This keeps the block from cracking.

I have the same leak anyone figure out what this could be?

Thanks in advace.