It's not that hard to replace that O-Ring. Did mine this year. It was available at Napa for less than $5. The idiot before me gouged the shaft by trying to remove it with the shaft in place. Don't do that, as I had to braze in new metal to make it work. Anyways, I would plan it for the next time you plan on changing the oil and filter because you will have to drop the pan. After that it is litterly one nut to pull the shaft inside the transmission. Make sure you get a mental picture of how it goes back together. Also, be prepared for some more oil to come out when the shat is pulled. Piece of cake.