1996 C280 fuel gauge / sending unit

96 C280 (82,000 mi.) fuel gauge just started to dance all over the place from empty to full with any amount of fuel in the tank. The gauge mostly sits on empty and seeks a higher reading for several seconds and then returns to the empty reading. I have read of different fuel brands possibly causing this problem but believe I am going for the sending units. I see left and right listed w/ and without pump and wonder if the offered OEM or after market units are recommended as replacement for the MB parts. I am looking for proceedure for removal of the sending units as this is my first MB.
Thanks