Inspect U-joint to determine if snap rings or nylon injection is holding the bearing cups in. Mark orientation of part so part can be reassembled in the same position. If snap rings are present, remove them first. Then support lower ear such that the bearing cup can be pressed out into a receiver.
Do not heat yoke.
Do not try to press U-Joint through both ears.
Use a C-tool similar to what is shown and press the bearing cup out, one at a time.
After all bearing cups are removed, clean the grooves where the new snap rings will be installed.
Start one bearing cup assembly into the yoke, install the cross, being careful that none of the needles move out of position during install. Install bearing cup to the start of the snap ring groove (final press will be done after both bearing assemblies are in place).
Turn assembly 180 degrees and install the other bearing cup assembly. Now press bearing assembly so the snap ring can be installed and repeat for the other side. Make sure snap rings are seated in position. The cross should be able to rotate.