Changing oil on RXV rear end

[Jerj7907]

I am really particular when it comes to oil and my vehicles. I like to use synthetic fluid if possible. The other day I parked my lifted cart and noticed some oil dripped out of what appears to be a breather vent on the axle tube just to the left (drivers side) of the differential. I checked and don't see a way to check the fluid level. Is there a way to check the level or do I have to take the entire rear end out due to the fact that the pan is facing almost directly down. Also if oil is changed is it a standard gear oil like 90W, it has the smell of gear oil.