Hi, I don't know if anybody will still read this, but I had a problem with my Land Camera 180 myself, one of the aperture blades was stuck right in the middle. Probably from the WD40 I got in it when I tried to make the gears work again... bad mistake but it is working again now.
Anyway, I was looking for instructions on how to open the front of the lens to get to the aperture and stumbled over this thread. It turns out John Koehrer was almost right. You need to unscrew the decorations ring. It does not come off but it actually IS the barrel containing the two front elements. I could turn mine just bei pushing to the outside with my two fingers and turning it. It takes quite a few spins.
Theoretically you could then also remove the rear of the two front elements but it looks like there is some glue in the thread. Made me think they might be glued to stay in a certain position, so I didn't try, although there is some dust in between. Probably would have required some gentle violence since I don't have the right tools. I was quite happy I could put the aperture blade back in place (basically just pushing it out gently until it "clicked" back into place) and didn't want to take any more risk. Maybe I wil try some other time. Just removing the front elements is quite fast when you know how.