a farmall rear end oil leak

I have a leak and a noise problem. I recently rebuilt this a and this weekend was the first time it had been driven. It is leaking oil from where the real axle housing and the transmission bolt together. I assume that this is probably an oil seal, but when the tractor was driven and high speed there is a knock like a bearing is going out from the same side. Has anyone ever replaced these before? How hard is it?? Any advice? Thanks

I was able to take off an inspection place and find a bearing out. After looking at my manual it would be the Differential Shaft ball Bearing, and the Differential shaft pinion oil seal. Would anyone have a NAPA cross reference number for these??

NAPA's web site can cross a lot of bearing and seal numbers.