Front TTB Fluid Change

I am wondering how to change diff. fluid on the front axle of my 92 Bronco FS. I had it out wheelin last year and noticed some fluid under front axle once i got back onto tar, found fill plug and removed it, there was alot of the sandy mud i had been driving through mixed with the gear lube. Does this mean there is a leaking axle shaft seal or something? Also cant find any drain plug and cant remove any diff cover like other axles. Not familliar with this type of axle, any info. would gretly help the ole Bronc.