Keep your fingers crossed that it's the lower, the upper cost 6x as much. Yes, the lower are more common.... figures it's one of my uppers that died. Definitely check them before you just start ordering parts.
On the topic of the upper ball joints, does anyone know if it's either possible to or if anyone has had a set of control arms machined to accept a replacable ball joint? I'm looking for a used control arm with a good ball joint and figured that if it 1) could be done safely and 2 could be done for the cost of or cheaper than a regular replacement, it'd be more than worth it. Finding a good joint to use and ensuring structural integrity are the issues.