Ok, looks like your machine has a 3204 engine. Like most CAT engines there are different configurations used dependent upon the machine it's in. Based on what I can find your transfer pump should be a plunger type pump located on the side of the injection pump, like the one, in drawing, in the link below. If that's what yours has then changing it is simply a matter of removing the lines and a few bolts to get the old pump off, and reversing the proceedure to get it back together.
I found the pic by doing a Google search for 3204 CAT engine. Within the results are links to posts on other sites where guys are having the same problem. One even had the injection pump rebuilt trying to solve fuel leak into the crankcase, with no luck according to the post. That said, a leaking transfer pump is a very common cause of the problem your seeing, but if that doesn't fix the problem it appears it could also go as far as seals on the injection pump shaft leaking, although I've never seen that personally.
Before buying a replacement pump give the guys at off Road Equipment a call. They can usually get either aftermarket, or NOS/OEM CAT parts much cheaper than getting them straight from CAT.
Again good luck.