So, Thursday, Friday, and now Monday, they're still working on it. The two main things I took it in for was the rear wheel speed sensor, and a charge air temp sensor. The temp sensor is brain-dead easy to replace, but the code came and went and I wasn't sure if it was just a sensor or a wiring issue.
Turns out, after 2 hours of intense diagnostics, it's just the sensor. They didn't have a sensor in stock, so they ordered one overnight, and it got sent to Florida instead of Bentonville, AR.
The wheel speed sensor, after 2 hours diagnosing that, yeah, it needs a new one. After a day and a half of fiddling and soaking, it's gonna have to be drilled out.
So I've practically moved into the MB dealer here.