Complex sentence: By summer of 2008 the patrol will have completed it's transition to the Smith & Wesson M&P.40 which retire the 4006 which has been in service for the last ten years.
Split into simpler sentences: By summer of 2008, the patrol completed it's transition to the Smith & Wesson M&P.40 which retired the 4006. The 4006 was in service for the last ten years.