Synthetic 75w140
It is on top of the center of the rear axle.
The 1500 4X4 went to the independent front axle in 2002. The 2500 and 3500 4X4's still have a solid front axle.
Yes
75w90 synthetic gear oil.
Begin by removing the tire and wheel from your 2002 Dodge. Remove the end of the axle. Remove the wheel bearing nuts. Remove the wheel bearing. Reverse the process to install your new wheel bearing.
To change the rear axle fluid you can remove the rear cover from the axle and drain it that way. If you don't want to remove the rear cover you can use a pump and a hose to drain it through the fill hole.
2002 - 2005 Ram 1500 will bolt in, but you need to match the correct ratio.
The 9.25 axle holds about 2.5 quarts. If you have limited slip you will need 4 ounces of additive.
If same body style, same size (1500, 2500, 3500), and same axle ratio, yes.
If there is not a drain plug on the bottom of the differential then you will have to remove the cover. Be sure that you service it with the proper fluid and positraction additive if it is a positraction differential.
The vehicle speed signal comes from the ABS sensor on top of the rear axle.
It is on top of the rear axle.