I did my own repair as well. With the service manual in hand for my Sanyo PLV-Z700 it was quite easy to disassemble and change the part. In my case I confirmed that the Blue Polarizer had severe burn. In bought a new Blue Polarizer and replaced it. The picture was greatly improved, but the yellowspot was still present, just not as noticable as before. In my case I now believe that also the Prism array holding the LCD's could have some burn damage. changing anything in the prism array concerning LCD's would be very cost full, so it's either living with it or replace the projector.
Anyway, I surely get tired of projectors before I even consider replacing it