Go to Advance or Autozone and "rent" one of their tools. It will cost well over $100 but you get it all back when you return the tool. You will get a full set and a quality C press so that you can get the exact pieces that you need. I just did mine a few weeks ago and I seem to recall that I used the press on the lowers with the top portion of the threaded rod inside the hole left after taking out the upper ball joint. If I would have had the Jeep higher off the ground, the press would have fit with the threaded rod on the bottom which looked like it would be more stable. But both ways should work.
Also, does your new lower ball joint have a grease fitting? Mine did and I had to install the zerk fitting, grease it, and then remove the fitting and install a plug so that the axle clears.