Walmart might take forever, but on the flipside, you can do some shopping. I'd rather do that than sit at JL.
In other words, I'd rather some guy making min wage move at min wage speeds, but doing it more or less correctly, than some guy making min wage while under the gun to get people in and out--horrible of me to think that way, but hey, I just want it done right. Either place can screw it up but I think Walmart might be less likely and more likely to make it right if it goes wrong.
But if you have a local mechanic they might be willing to compete. I wouldn't rule them out. Might be worth a few bucks more if it builds a good relationship, after all, own a car long enough, eventually it needs something that neither place can do.