Jim,
On the 280 engine, you use a 17mm crows foot wrench for the fuel line. I think it the same for a 250. The MB number is 000 589 68 03 00. Hazet # is 4550-1. It is a nice tool to have but in a pinch, just use a crows foot wrench. Classic Center has them and was surprisingly reasonable. Is available from other sources but some can be $$$$$$ for the same tool. The 2768-1 is the crows foot wrench used to adjust the valves. Also a nice tool to have. I don't think that one will work here because there isn't enough clearance for the fuel line. The 2768-1 is a heavy duty wrench and maybe too fat to get in near the valve cover. The 4550-1 is more dainty and not meant for a high torque. Should be able to find a picture on the web for 4550-1.
Once you get the fuel fitting off, you use a 19mm socket to remove the injector. When removing the fuel line, try to hold the 19mm injector body with a wrench. That will prevent the injector from turning and in turn binding the fuel line. Make sure you torque injector and fuel fitting to specs.