If you wrap around the building, the entrance to the service desk will lead you inside the Walmart. Careful, the door locks behind you unless a staff member unlocks it for you. Alternatively, you can walk from the front entrance all the way through to the back left. That will take you about 5-10 minutes to walk given if you're browsing or if it's busy.
You can make appointments ahead of time or drop-in. I dropped by on a Saturday at about 11AM to get my tires swapped, but didn't get it back until 2PM. It's not so much that the mechanics are slow, but they placed gets swamped and it seems like they only have one person at the time working the counter. So for example, your car could be done 20 or 30 minutes before you're even told because the counter worker is also busy checking in 5 other customers. Just a head's up! read more