Regular odometer is all that quit functioning.
The odometer and trip odometer can be replaced but you have to essentially disassemble the entire speedometer but that's difficult. There are multiple small screws that need to be organized as you disassemble, some have machine threads, others coarse thread that screws into the plastic, different lengths and diameters.
The plastic cover, speedo needle, and gauge face must come off. The push button for the trip odometer unscrews. The speedo needle is on a splined shaft and pulls off.
The trip odometer can be replaced as a unit. The odometer that registers cumulative miles is removed with the numbered wheels on a skewer of sorts, plus there are small tabs to prevent reordering the numbers. I found that the 1/10s wheel had a stripped gear and that's what stopped my odometer from recording. The rod that supports the odometer sits in that plastic housing. Once the trip odometer housing and speedo drive have been removed you can slightly squeeze the plastic housing and align the narrow portion of the rod with the notch and lift out the odometer cluster.
I now have functioning odometers but the speedometer doesn't work, I did not reset the needle properly.