I can't remember exactly how the Tacoma diffs are set up, but if that is the only damage then this is my suggestion.
Rotate the carrier until the end of the cross-shaft is visible, there should be a bolt visible that looks like it bolts into the cross-shaft, if not visible, rotate the carrier around 180* to find said bolt. Back that bolt out and with a drift of some sort you should be able to pop the pin out. The offending gears should be able to be removed and inspected without disturbing the carrier. I agree that you should be able to find a used gear relatively inexpensively. I would call up a local 4wd drive shop to ask if they have any laying around. Most 4wd shops or the like just chunk them when they do lunch-box locker installs, so call around. I think I gave $10 or $20 for a pair.
It should go back together in the reverse order. Before you go messing with the carrier bearings, I would make sure you have a dial indicator and a base to keep up with the backlash settings. I got mine from Harbor freight for a decent price.
As far as the pinion bearing preload, if you are going to pull the seal, you can go two ways. The quick and easy way is to mark the nut, back it off, replace the seal, reinstall the nut and tighten it slightly past the original staked location. The more better way would be to get a new nut and a solid sleeve, remove the nut, flange, outer bearing and crush sleeve. measure the crush sleeve and see where to start your pinion preload shim stack at. Install the sleeve, shims and outer bearing, tighten it down and check preload (it is in IN-LBS, so you will need a different torque wrench for that), adjust the shims until you hit the preload number, then remove the flange, install the new seal and put the flange on with the new nut and put about 100 ft-lbs on it with some loc-tite and stake the new nut.
All this sounds terrible, but it really isn't as bad as it sounds, just make sure you have the right tools and take your time. Unless you have a press and really want to get into it deep, you are not going to be able to adjust the pinion depth since that requires messing with the shim stack on the head of the pinion. But the pattern is probably good, you may just need to tighten the carrier bearings to put a little preload on them.
ZUK's page is an excellent resource and is where I learned what I have and where I gathered confidence to start fiddling with them myself. I did pretty much what I just mentioned above to a diff that I replaced in my 90 pickup and have put nearly 100k miles on that used diff. I just got my own press and a bearing splitter, so I don't plan to pay anyone to do diff work anymore. I have fixed to many that were "professionally" done.
Also, unless there is visual damage to a bearing or you feel a "flat spot" when you roll them around then I wouldn't worry with replacing them. Just a new seal and a solid spacer along with the new spider gears and you will probably be good.
Good luck.
