2.5TDI oil leak at water pump!!

It's not as bad as it sounds. On the 2.5TDI Discovery (1991version), the top stud in the water pump appears to also have oil pressure behind it. I found out when I accidentally stripped the thread at the inner end of the stud. I managed to get it back in but over time it has come loose and now leaks oil down the front of the water pump and subsequently onto the already heavilly oiled drive way. Does anyone have any suggestions as to how to stop the leak. I was thinking take the stud out, re tap the hole, de grease the whole thing and locktite it all together. I don't know what size tap either. Hope this makes sence and someone can help me out. Thanx Gary