I recently replaced mine on a 2004 marquis garnett. Mine was not rebuildable as the latching mechanism bent. I fist called monaco and got a price of $1400 could not order only the front had to buy front and back as a pair. Next I found a salvage yard for $300 plus shipping at
http://en.visonerv.com/ I don't know what style lock you have, but on my coach the slide lock style was riveted, the replacement part was not riveted which was much easier to install. If yours is not riveted you can easily remove one screw at the top and lift the lock about an inch to remove.
On the riveted lock had to drill and grind all rivets for removal.
Lots of Luck
Steve