It's just a guess, but I'd say that the Blue LCD panel has issues. I don't suspect a burned polarizer as those issues do not change shape. And there is no way that a lamp will be cause of any localized image anomalies. The only issue you will see from the lamp is OVERALL reduced brightness/contrast.
The cost of repairs far outweigh the cost of replacing the projector. Considering that the unit was discontinued in 2005, it's a safe bet that anything you get now will run rings around your old unit.