I don't know if you can rent a ball joint press at a parts house or not.
The tool you need looks like this
http://www.harborfreight.com/cpi/cta...emnumber=38335
That one is a knockoff of the OTC brand one I have which I see has gone down in price a lot since I bought mine.
http://www.ntxtools.com/network-tool.../OTC-7249.html
With one of these you press the old ball joint out and press the new one in and it works slick. You want to grease up the threads on the screw pretty good though.
The C clamp part works great for changing U-joints and I use mine for that all the time.