In that case I would not be surprised the 3mm spacer ring is already installed.
About the condenser, after removing your AN glass, the black bayonet ring and the spring: use two fingers of each hand to press to the outside of the opening and lift it up. It is very easy, just pull it up and make sure it does not drop down. You need medium warm water with some dish washing soap and a totally soft sponge to clean both sides of the glass. Then rinse with the same medium warm water and use a soft cloth to dry everything . . . when putting it back use a good light to see where the two pins slide in and bring it down in the same way. A clean condenser is a must.