Sorry to hear is. In my experience, opening a Shimano pedal is the kiss of death. Once opened- they will die in 6 months.
I guess I will be testing that theory.
I have a 7900 set that was still very smooth, but was in fact so frictionless that the pedals wobbled around wildly and made it difficult to clip in.
I had just come off experimenting with the Look Keo Blade 2, which doesn't rotate at all when unclipped, which was actually easier for me to clip into because they stayed in the position you last unclipped.
So I removed the spindle assembly from the 7900 set (just as shown in the Park Tools webpage instruction) and jammed the bearings full of a heavy marine grease without removing the bearings from the spindle assembly. I then pretty easily adjusted the bearing preload so that they are smooth, with no play or noticeable bearing drag.
It seemed successful; it "quieted down" the rotation of the pedals, but they are still low friction and smooth, just a lot more viscous. It was really quite simple with 20mm and 17mm cone wrenches. We'll see how long they last now, and I will report back.