Simple Remove and Replace.
For the Endcap (right side with the temperature control) the only tricky part was removing the sliding temperature control arm & reattaching to the rear housing. The arm and the sliding Temp Control Knob are not included with the Endcap so you'll need to re-use or order new ones. The Endcap is connected to the housing at a 90 degree angle at the rear of the unit. To detach, squeeze the housing on the rear vertically to free the Endcap. You can then twist the joint where the Endcap arm meets the rear arm to release the tab.
For the Center Rail it's a simple drop-in. Remove the crisper drawers and the glass shelf above them. It's easiest to remove the shelving Frame next (lift at the front to release from side pins then pull straight out). Once the shelving Frame is out you can flex the rear to release the Center Rail and it drops right in.
Easy-peasy, and thanks to Appliance Parts Pro for saving me so much money over the years with parts and helpful video instructions.