Sony KDS55A2000 optical block rebuild?

I have read there are rebuilt optical blocks available, rather than shell out $1,000+ for a new one. Anyone here have any idea what is involved with rebuilding them. I repair TV's as a hobby, been doing it for several years now, so I assume I could do this. I should point out what's wrong with the set. It doesn't have the green haze issue, but my buddy (his TV) said he saw several small yellowish patches around the screen, which really were visible with a solid background color, such as grey. This morning he told me he doesn't see this now on the TV, but in the event it is the block, I hate to see him have to trash this three year old set. As always, thanks for any info or suggestions.