1994 volvo radiator leak: what part is this?

[snowing]

Hey All -

I have been noticing a small amount of fluid under my car in the mornings. Based on its color, it appears to be coolant. The only sign of a leak that I can immediately find is the part in the photo attached. I believe this is simply the radiator plug. Is this correct? The part that is leaking is the round, black plastic protrusion on top (though the photo appears rotated to the left here). You can see a glint of coolant around the seal.

I am not losing a ton of coolant, but the level is now starting to get a little low. However, I also notice a strong burning plastic smell suddenly that seems intermittent. Is there a logical connection between these two things? Is replacing the plug as simple as pulling the old one out and slipping the new one in?

[lummert]

In cars with the mechanical fan, but with front pusher fan, a fan temp sensor goes in that location. Maybe the rubber seal needs inspected or replaced.