how to change plugs and wires on the back side of engine?

Very carefully! In some cases it may be necessary to remove the alternator on your 1992 Dodge Grand Caravan to access the rear spark plugs. Sometimes working from the bottom is also helpful, it just depends on the specific vehicle. What is boils down to is that you must remove whatever is in the way in order to access the back spark plugs, there is now "easy" way.