Product review (5 stars): How to replace ROLLERS for Whirlpool Refrigerator model G2IXEFMWS00
I did not buy this at Amazon. I mistakenly bought the front roller but I needed to replace the rear one, and was able to retrofit it. Here are installation instructions in case you, like me, find the ones that came with it to be a little too brief.

For front roller part # 2166108, or rear roller part #2150304, for Whirlpool Refrigerator model G2IXEFMWS00

You need 2 people for this job - primarily when tipping the fridge and propping it up.
1. Unplug refrigerator or turn off breaker to the outlet it is plugged into
2. Unload all contents in the refrigerator/freezer and remove door shelves (interior shelves can stay in, although it is best to make the refrigerator as light as possible)
3. Roll the refrigerator out from the wall until you have enough space to walk and squat behind it. Since you have a broken wheel, try to lift it up at that corner so you don't damage your floor.
4. Remove the plastic grill at the front floor level. To remove filter cover, twist  turn to left and pull.
5. Remove the plastic bolt cover for the freezer door bolts at the top of the cabinet
6. Remove the  three freezer door bolts and lift the door off the post (5/16")
7. There are 3 bolts holding the refrigerator door on (5/16"). Remove the inside most bolt. Loosen the other 2 bolts on the outside edge about ". Once loose the door will twist and lift off.
8. Lower both level adjustment screws at the bottom front sides by turning left. Remove them completely (3/8")
9. Remove the rear bottom cardboard/particle board cover at the bottom of the back side. You can remove all screws (1/4") except the one next to the electrical cable, and you likely will have enough room to reach behind it. The rear cover should flap freely.
10. Remove the 4 bolts (1 at each front corner and 1 at each rear corner) that hold the base plate on. (3/8") Once these are removed, push the base plate toward the back about 1 inch. At that point, it will drop down.
11. Tip the refrigerator up on the side where you need to replace the roller by propping it up on one 2x4 (1 "). Make sure the 2x4 is only under the lip of the outside box and not under the base plate.
12. To replace FRONT ROLLER , push down on the base plate until it extends about 1" below the bottom of the refrigerator. Reach fingers inside from the front, and push the pin out that holds the wheel assembly, remove the pin, install the new wheel assembly, and replace the pin. Make sure the wheel is pointing down (rotated toward the front) and not pushed back up in the cabinet. To replace a REAR ROLLER, you should be able to push the base plate back far enough to access the pin without pushing the plate down. Play with the base plate to line up the holes for reinserting the pin.
13. Lower the refrigerator back to the floor.
14. Push up on the base plate from underneath in the back, while pushing it forward. It needs to come all the way forward so you can see the base plate up against the bolt holes that hold the plate in the front.
15. Reinstall all 4 corner bolts for the base plate.
16. Then reverse the directions going backward from step 8, and you are done.

This document shows the door and roller parts (Cabinet Parts) and the base plate (Unit Parts)
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