u can unplug ur cluster, it wont reset ur mileage. the only reason it would reset ur mileage is if you put on a new gauge cluster. you can take off ur stock gauges, by removing the needles first them pulling the stock gauges off. it wont reset ur mileage, dont worry.
*2003 Black GT-S 6speed* TRD body kit, HID upgrade, clear corners, Matrix XRS shift knob, 02 tails, trd exhaust, AEM gen 2 CAI, TWM short shifter.