How do you tell which side is front and rear? On my old or the new one nothing says front or rear? The flanges that attach to the driveshaft and transmission...........would it not be very hard to mess this up as the flanges fit inside the transmission yoke and driveshaft yoke, right?

If the unit has been installed backwards, is it now damaged?

The mechanic did use the new bolts as the new ones were large allen head and the old ones were standard head. He placed the washers like on the driveshaft yoke, they were placed on the bolt side and not the nut side and vice versa on the transmission side.
So on the driveshaft yoke the four nuts were screwed down with the washers below the bolt head and not on the nut side. THE NUT IS SCREDED DOWN DIRECT TO THE YOKE. Is this correct?

Thanks for any input as I need to get the car back to hime first thing in the morning.