I would just keep it man, with the high miles and such its gonna run like a top for a long time if you keep up with the maintenance. Price range Idk maybe 6k if you can find a buyer who wants the manual? Sport package is a plus when selling but remember its a 13 year old X with a not widely desired (unless enthusiast) transmission.

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2018 Ram 2500 6.7L Cummins 68RFE
19k miles -Bright White/Black - Big Horn Sport - Crew Cab Short Bed
2013 X5 35D (CEO's) - Born on 5/17/2013 -
82k miles - Alpine White/Cinnamon Brown/Premium Pkg, Sport Activity/Premium Pkg and Sound/20" Style 214/Running Boards