It wouldn't be a bad idea to replace the rear main seal anyway. Its about 7 dollars when I bought it and it definitely helped with my leak. Imagine a red jeep going down the road and smoke bellowing out of the back. I replaced it and it was good to go. Simply put, just lift the jeep, drain oil, remove oil pan, remove rear main seal cover (a big block of metal held by two bolts), push gasket out and lightly oil new gasket, insert and you should be done. The old gasket might stick so you would need some minor tools to scrape it off.
When you are here at this point, I would also replace the oil pan gasket too, it'll come loose and torn up, use the rubber not the cork, IMO I think it's better, reverse order of steps and go for a drive.
If there is anything else that you need to do at this point, I would go and do it now since you have everything down, such as replace the oil pump. Hope this helps, it's alot less expensive. I called a shop and they wanted to charge me about 300 dollars and a week with the jeep. It took me a few hours, of course I took my time too.