The process above with pictures> CumminsDatabase.com :: 12V Dowel Pin Repair
If you want to make it easier
Most Cummins shops no longer remove the cam when replacing the case, cuts about $600 off the bill. By not removing the cam you don't have to take the front end all apart, remove valve covers or fool around with wooden dowels.
After the timing case cover is off turn the engine till the line up marks on the gears are lined up. A high quality three prong puller (Snap On is best) is used to remove the gear off the cam but there is also a special Cummins puller made just for it that works way better. The gear goes back on by heating it and sliding it on to the cam.
The gear can be heated in two ways, 1) Toaster oven, next to the truck so the gear does not cool down: 2) Propane space heater, one that can have the elements turn up like a grill. Set the temp around 300 F. The oven is the easiest way, depending on the oven it could take 30-45 minutes to heat up, in the meantime you can clean some parts. The propane heater is faster about 10-15 minutes.
You need an extra hand for a few minutes to hold the cam from moving back and pushing out the rear cam plug. The cam is held by removing the fuel lift/transfer pump (don't drop the pump actuator arm into the crankcase!) and using a pry bar on the cam lobe, apply a little force to move the cam toward the front of the engine. The cam can move slightly but all you want is the cam not to move back when the gear is going back on. Once the gear is up to the temp, the crank and cam timing position has been set, someone is holding the cam from sliding back, you then grab the gear with high temp welding gloves and slide the gear back on, sometimes might have to tap it back with a plastic mallet or dead blow hammer but never with a steel hammer. I've done this three times and never had to use a hammer, the gear slid right on.
I would only recommend this to someone with mechanical experience. Sounds a little complicated but is way easier. There are three draw backs: 1) gear cooling down half way, then you have to wait 10 minutes to cool and remove it again to start all over; 2) Not aligning the crank and cam; 3) Allowing the cam to move back and pushing out the rear cam plug, then you will have to pull the engine.
Some people think this method causes a weaker fit for the gear but Cummins has been using this method exclusively for several years, I've never heard of a problem