The ball joints in the upper OEM control arms are not replaceable, you have to replace the whole control arm.
Be careful if you purchase an OEM type as there are many cheap knockoffs available like Crown and they are junk and will not last.
Some of the better OEM type brands to purchase are:
Mopar, PN 68068615AB
Moog, PN CK3198
or if you want the best as metalengineer suggested, purchase the upper control arms from JBA (Jeepinbyal) that have serviceable and replaceable ball joints.
https://jeepinbyal.com/liberty-2002-200 ... -arms.html
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