Heater Core Flush?

Hey everyone. This is my first real post and pretty much why I joined. I'm hoping for some good advice as I keep my '07 Frontier for at least a few more years (cross fingers). Anyway, here is my issue.

Recently I started noticing the scent of anti-freeze. After checking things out, I discovered a leak around one of the heater core hoses (see pics). I don't have anything leaking in the interior of the truck. It appears to just be from that hose. So, a couple of questions:

1) Is it possible just flushing the heater core could fix my problem?

2) What exactly is that plastic connector that the rubber line is going into and the metal pipe going off to the right?

3) if that plastic part is some sort of valve, could it be blocked or malfunctioning and need to be replaced (instead of an issue with the heater core)?

Thanks!