On mine, it was easier to remove the rear lens element with the whole shutter out of the camera, but that opens up another can of worms. One of the tricky bits with this camera is that there is a spring that applies pressure to stop down the aperture blades. Looking inside the shutter box from the rear you'll see a star wheel in the lower left. There is a set screw that you remove and then the star wheel will unwind to release the spring tension. See some of Jon Goodman's and Rick Oleson's info linked below.
Here is a good flickr set that illustrates going in from the front:
More helpful info:
The middle element can be unscrewed from the front with the front element removed. This will change the "starting point" for the threads on the front element though during reassembly, so there will be a little trial and error there. Again, I found it much easier to work with the shutter completely removed from the body. With my moderate skill set, several of the steps took a few tries and much patience. There's a lot that needs to happen when you press the shutter on these things.