I am fairly certain that the EC65 and the EC75 use the same casing (maybe just more /bigger filter fingers), so it should be a direct swap. As I recall installing the EC-75 was trivial, just pull it out of its box and sit it on the base, connect the plumbing and screw in the pressure gauge and add DE through the skimmer. Mine was bought off ebay as a combo set with a 1.5 HP Super Pump, and base plate, I know it is also commonly sold with the 1 HP Super Pump so there is some room for variation, I opted for the 1.5 because it was identical to the previous rusted out pump. The biggest issue you will likely have is your plumbing lines, are they all glued together and have to be cut out, or are there removable fittings to allow the pipes to be removed from the filter?
Ike