Is my Lego Star Wars "Jabba's Sail Barge" set a one of a kind? Back in 2006 or 2007 I bought a Lego Star Wars "Jabba's Sail Barge" set. When I opened it and took out the instructions, it had an additional piece of paper. It showed that the piece 4299023  had been replaced with a normal solid piece. I am writing to ask if this makes the set I own worth more, as it is rarer, and is it desirable ?
The short answer is no, this does not make your set more valuable.

You have recieved a set that contains what Bricklink calls an "Alternate Item".  These are alternate pieces/stickers/colors/etc. that are packaged into normal sets by LEGO in order to ship out the sets in the event of a part shortage.  They are perfectly normal.  And, usually, they are more common pieces than the pieces they replace, so there is no added value for the part.