The C clamp style press mounted in a vise is the easiest way to change the U joint. Use a lot of lube on the threads of the press or they will gall, especially cheapo presses. I would inspect the thread and run them full in and out before leaving the store with a rental.
I also have a hydraulic Cclamp style but prefer the manual thread with an impact.
H frame presses work but is harder and can have too much power if you are not careful.
I do not heat them, a good press will press the joint out with the plastic in it.
The critical part is to keep the needles in place, a little harder to do when hammering them in.