I just got another Olympus Pen, this time a Pen W with the black paint. The price was a little low, and when I recieved the camera I found a couple of problems.
First, the original Olympus filter was stuck on, and wouldn't come off. Turning the filter cause the entire aperture/lens assembly to turn as well, and the entire front lens assembly was loose.
Next, the viewfinder was quite foggy, and hard to see through.
I took off the top cover and remved the dust cover from the viewdinder assembly, removed the screws, and pulled out the assembly in one piece. I then soaked the glass elements (and the glue which holds them in place) with paint thinner. Once the glue was loose, I gently pulled out the elements, cleaned them, and then glued them back into place.
To repair the lens, I removed the three set screws which hold the focusing ring in place, and turned the ring and lens assembly leftwards until it fell out of the camera. I found that the circular nut which holds the lens in the collar had backed out. I tightened the nut, and then using a couple rubber wrenches, I was able to get the filter off. It appears the filter has never been removed, the front glass had no marks at all.
There was some haze on the rear of the front element, I removed the element and got the haze cleaned out. The aperture blades had no oil on them. I pulled out the entire shutter assembly, cleaned it out, dried it, and lubricated the mechanism with fine watch oil.
Putting the camera back together wasn't so difficult, but I had to set the lens to infinity using a ground glass and loupe, then set the focus ring to the infinity mark, and tighten the set screws. I also put in some new seals while the top cover was off.
The camera is now back together, and works beautifully, the shutter tested within 1/3 of a stop, which is close enough. I am shooting some film with it now, along with an Olympus 35 Wide S which I also recently bought.