A picture would be nice, but haven't seen to many that you would have to remove the hyd. pump, to pull the distributor. I had a 2424, 20 years ago for a short period of time, but can't recall just how close things were. But going from this diagram:
Schematic, Manuals, Specifications and Diagrams for Battery ignition unit | Case IH | MyCNHi US Store Looks like removing a couple of bolts, holding the base clips in, it should pull out.
There should be a small roll pin holding the drive gear on the shaft. If it has not sheared, than the next weakest link would be the distributor drive shaft,#8 in the exploded view. Running the part number through Google, and as many hits as I got, that may very well be the culprit. I got 4,920 hits, so apparently this has been a problem child.
Being there are teeth on the drive shaft, it will have to be timed. Use the basic #1 on compression stoke, and get it to TDC. I'm assuming the TDC mark is on the crankshaft pulley. If it is the driveshaft, align the tang end, and insert. Normally,#1 on the cap is top right. You can make a temporary mark on the base, where #1 hole is on the cap. Insert distributor, and with cap off, set rotor button pointing at that temporary mark. That should be close enough to start. Should be able to dial in the rest of the timing using a timing light. If he has a service manual, it should give the timing specs. If he doesn't, might be an idee to get one, or, you may find it doing a search, for timing the C-146 engine.