Yes, The decorator ring is the one with the information on the front of the lens.
Get a rubber stopper at the local hardware. Take the lens with for sizing. When you have the stopper press it against the ring and push counter clockwise. If the element protrudes too much you may have to gouge out a depression in the stopper to clear the glass.
Sometimes I've used PVC pipe with an O ring to get a stubborn one apart.
On the back there's probably a spanner ring under the mount but I'm just guessing on that one. Look for a set screw around the base.
I don't know what the three screws in the mount are holding but if you approach it carefully you shouldn't have problems reassembling it.
Take some notes & pictures as you go along for reference.