do you have an auto parts store where you can get the code read for free and maybe they do the print out of the code too for free???
Then you could go online or look through the CD rom manual and pick your brain???
If the oil spilled on the sensors going into the hubs/disc breaks then that could have shorted them out making the light come on and flash.
The oil is in the right spot coming out of the filter to spill out and run out and perhaps run down the sensor on passenger side. It's a long shot, but IF they are a really sloppy shop it COULD happen.
Or maybe they are one of those shops that MAKE something happen and hope you are going to pay them to get it fixed. Or fix it elsewhere and that place will do the same and hit or miss they will get it fixed at your shop. Scandals.