Are you sure the differential breather isn't clogged? Once it's plugged up...pressure will build up and blow out gear oil from the seals as the differential heats up. Looks like the breather is located on the front of the differential near the 4WD actuator. It should be either a 14mm or 12mm wrench to take that breather off. You might want to think about putting a breather extension hose on there. I have a post about putting one on the rear here somewhere with piccies and part numbers. 
Looking up a 1997 T-100 4WD on www.toyodiy.com, the part number fer the seal is 90311-35032. Seal is fer left or right side.
From www.toyotapartsales.com this is what came up...
9031135032 $13.03 $0.00 $9.41
Front drive axle - Drive axles - Front axle - Output shaft seal
Output shaft seal, t100 - 4wd two piece housing 1995 - 1998
I would recommend that you git a hold of the factory service manual. It has some really good detail on the T-100. I just noticed in the front differential section that it doesn't mention the snap ring fer the side gear shaft until you git to the reassembly section. I guess that's why you'll need a slide hammer to pull that side shaft out of the differential.
Part number fer that snap ring is 90521-29002.
From www.toyotapartsales.com this is what I came up with...
Item Number MSRP Core Price Price
9052129002 $1.09 $0.00 $0.78
RING, HOLE SNAP
Looking up a 1997 T-100 4WD on www.toyodiy.com, the part number fer the seal is 90311-35032. Seal is fer left or right side.
From www.toyotapartsales.com this is what came up...
9031135032 $13.03 $0.00 $9.41
Front drive axle - Drive axles - Front axle - Output shaft seal
Output shaft seal, t100 - 4wd two piece housing 1995 - 1998
I would recommend that you git a hold of the factory service manual. It has some really good detail on the T-100. I just noticed in the front differential section that it doesn't mention the snap ring fer the side gear shaft until you git to the reassembly section. I guess that's why you'll need a slide hammer to pull that side shaft out of the differential.
Part number fer that snap ring is 90521-29002.
From www.toyotapartsales.com this is what I came up with...
Item Number MSRP Core Price Price
9052129002 $1.09 $0.00 $0.78
RING, HOLE SNAP