Finally decided to correct my Social Security card with the right DOB (guess it's been 1 day off since I was 12), and thanks to Stephanie K for directing me to the 2nd door furthest from the parking lot - guess it's pretty common for people to walk into the first door (benefits). The process was relatively quick and painless, I probably shouldn't have put it off for so many years since replacement cards are free.
Note that the benefits office closes at 3, but the cards side is open till 3:30pm and you just need to be in the door by then. My strategy for places like this is to go right before closing since they want you out as quickly as possible. Going by the numbers, there were about 40 people ahead of me but the line moved pretty quickly - I was out within about maybe 45 minutes, so going on your lunch hour is doable at least.
Office is depressing as hell, but it's clean w/ a lot of seating. There are guards on site and they were surprisingly needed to kick out a very angry lady and her elderly dad. I'm really not sure what could possibly piss you off at the cards office, but the guards were actually good at calming her down and let them back in eventually. They also made the 2 morons blasting youtube crap on their phone turn it off speaker, so yay for that.