MS290 Oil pump small oring & parts?

Replacing oil pump line on a bar oil leaking saw, and see a very small o-ring on the plastic tube that feeds the bar.
Also there's a plastic swivel piece that does not come with a replacement oil pump, and before I reassemble that pump, I want to know whether these parts need to be checked out before sewing it up.
Does that plastic swivel piece come apart easily and is there a gasket or oring in there?
I wasn't able to really discover where the bar oil was leaking from...not the cap, but it was grimey in the oil pump cavity.
 
Much appreciated info on this.