What is this that is leaking?

[Adam_]

Doing a coolant change on my 182 and noticed this cylinder is leaking yellowish liquid from it.

In front of the radiator, guessing it may be something to do with the air con system?

My questions:
- What is it?
- Easy/worth replacing?
- Should I be concerned?

Thanks in advance!

 

[mossyv6]

Air con dryer.