The first thing I did with the car was to pull out the PCB boards from the rear lighting fixtures. After doing this I could see that all the sockets had oxidized and was probably the reason why a lot of the lights weren't working. While the wife and I watched our show on Netflix, I scrubbed away at all the sockets and lubricated everything with a light coat of dielectric grease (this should prevent further corrosion or oxidization). I also took this time to test every bulb with my multimeter.
I set the multimeter to beep and detected every complete circuit on the bulb. This saved me $1+ per bulb. They all were good! I had planned on replacing them all. After I replaced every bulb I also tested each circuit with the multimeter to make sure current could make it through to the bulb.