I posted in the thread I started and didn't get a response. I need to find out ASAP what this part is so I can change it if possible.

What is the name of the round disk I am pointing too? Is it an expensive part and is it simple to replace?

Engine crankcase vent valve. Its like a PCV valve. Shouldn't take more than a couple minutes to replace.

Just as a matter of interest, why do you feel you need to change this part?

If it's starting to get blocked just take it off, rinse out thoroughly with paraffin and allow to dry, before re-installation.

Check out this thread.

Sulfur smell and rough idle

OES Genuine W0133-1826620 Crankcase Vent Valve | Auto Parts Warehouse

And the hose

OES Genuine W0133-1826576 Breather Hose | Auto Parts Warehouse

Do I have to purchase the hose also?

Well I think it depends on if the hose has a hole in it or not. It is pretty easy to disconnect (squeeze it) but the end on the backside of the motor can be tricky to get to. Take it off and check to see if there are any leaks in it. I'd prob fill it up with water, hold a thumb over one end, and blow in the other to see if it squirts out anywhere.