330d_Msport

I have just bought an E91 330d from a private owner. When I took this car to a BMW specialist for a thorough service I was told that the Sump plug was stuck in the sump! If it comes to a sump replacement, I've been told I could be looking at a bill of approx £400. Is this a reasonable price? Surely garages must come across this fairly often? Any help would be greatly appreciated.