I own one of those but never had to take it apart. However, looking at the parts diagram (
https://www.bachmanntrains.com/home-usa/dwg/dwgs/N_scale_2-8-0_Consolidation.pdf ), that looks like an easy task.
Drivers #2 and #3 (center ones) are geared, but driver #2 does not have a crankpin. Drivers #1 and #4 are turned by driver #3 and the siderods.
Looks like you will have to pull out the main crankpins on driver#3 (but observe and note the alignment of the eccentric arm at the end of the crankpin in relation to the center of the driver on each side), remove 2 screws from the bottom frame cover and pull the cover off.
Then you should be to pull out all the drivers. Drivers #1 and #4 will remain coupled by the siderods, but that is ok.
First just drop in #3 driver. Nothing needs to be aligned but it would be helpful later if either the counterweight or the crankpin hole on one side is in the most down position (looking as if the loco was sitting on the track).
Next, drop in #2 while visually lining up its counterweight (or the crankpin hole) to align with #3 driver. This might take few tries as you might end up with the #2 gear being off by one tooth in either direction.
Now add #1 and #4 set. The #1 and #4 can remain loose and out of alignment.
Replace the bottom frame cover and screws.
Now spin #1 or #4 (since they are coupled) until the crankpin hole in the siderod aligns with the crankpin hole in driver #3. Reinstall the main crankpin paying attention to the position of the eccentric. Don't forget to capture the main rod onto the crankpin The main crankpin is usually keyed some way (like the pin which goes into the crankpin hole in the driver is square shape or flattened. Then install the main crankpin on the other side, again paying attention to the eccentric location.
The loco should run as well as before it was disassembled. This is one of the easiest ones to service becuase no compicated driver alignment is needed.
