If the battery is at 11.9, it wasn't the starter and you three away good money. A brand new starter may perform for a little while on a dying battery, but in the end you will find out you should have replaced the battery and kept the perfectly good starter you already had. Now you have to pay for both.

 

On a 2008, the starter was long overdue anyway.

 

Overdue for what? Starters do not have expiration dates or recommended replacement schedules. They are replaced on condition. In dry climates they can last for decades.

 

I'm in a dry climate and mine don't usually last for decades. Usually the issue is the solenoid, on many units you can replace that separately but depending on labor to access the stater and availability it's often easier just to do the whole thing.

On the motor itself, the brushes wear, although that depends on driving habits, ie how often you start.

When I've taken them apart, there's often carbon dust buildup around the brushes/commutators. In many cases you could probably replace the solenoid, brushes, clean up the dust and be fine. Bearings and windings can also fail, but that's probably rare.

After I retire, I might get back to a place where I have the time and patience (and spare car) to rebuild starters and alternators