Installing new gears is no big deal if you have the necessary tools. The 8.25" mopar rear has internal hex adjusters to set backlash & if you don't have the long [~30"] hex wrench, it becomes difficult to finish the job. Ring & pinion gears exchange easily altho the pinion depth spacer is under the pressed on rear bearing cage & it should be removed to determine the original shim thickness [to compare with markings on the new pinion gear]. This requires a sturdy puller & press to seat the new bearing.

If you've done gear changes before the process is very straitforward: remove the old gear set, check the differential case for excess runout, install new ring gear & carrier bearings, install the new pinion, pinion bearings & new collapseable spacer, measure proper bearing preload & insertion depth [after replacing carrier], set backlash using a dial indicator, replace cover, fill w/syn 75W-140 & you're on your way!