Hidiy, Doug-
You should be able to get to it from under the truck or in the cab, but what is the truck we're looking at? (year/make/trans/etc)
Easy, less than 600 seconds job on some of them... it is not a complete transmission disassembly is what I mean. On some transmissions, there is just a capscrew to remove to access the little gear with a confusing nomenclature.
Brad