I found replacing the aft bilge pump was easier than the one in the center. In my '06, it was on the driver's side of the engine. Take all your stuff out of the locker, remove the panel by the engine and you shoulw be able to see it. The problem I had was the Rulee 750 changed shape. The new pump wouldn't fit into the old bracket. Fortunately the screw hole pattern remained the same, so I swapped brackets too.
2006 X-45 LQ9
2005 Yukon Denali