well maybe I explained the procedure for a free standing wheel, if there are 2 wheels within a few inches of each other between the slide rails, the wheels are on a common shaft that is bolted to each side of the slide rail, you need to pull the bolts from both sides and remove the entire shaft.
with the shaft on the bench there will be a spacer tube, a washer, the wheel, another washer, the center spacer tube, a washer, the other wheel, another washer and the last spacer tube.
Once you have the wheel in your hand, the plastic bushings are the same as explained the first time