Can you tell me what this part is,and is it expensive,and can I replace it?

[FlaAveo5]

Ok. So I have my car blow up yesterday on the beach, towed in and its the coolant connection broken away from the engine. But when I was manually wiping down the engine, it is covered in coolant now, even though I told them to clean it with engine cleaner....BTW...should I get the engine cleaner foam in a can, and clean the engine, or let it now be filthy? If I manage to post the picture of this part i saw that looks' rusty to me,I am hoping someone can tell me what it is and if I can replace it, is VITAL,or what. If the picture dosen t appear, it is a round part with a tiny metal tube in front of it, on top of the 4 plastic exhaust head? on top of the engine right in front of the firewall on top right at the rubber seal where the wipers are. Hope the picture comes out. Thank you.