Open the top (below the scanner lid) and the printhead will center itself in the access hole. Pop the two ink cartridges out. There is a tab on the frame that carries the ink cartridges, towards the front of the printer; pull this (or push?) a little and lift the arm up (pivots at the rear.) The printhead will lift out (do so from the rear, where the ink latches are... it comes out easier this way.) Invert the printhead... you'll probably see four shiny gold "ribbons," one of which will be blackened.
If the printhead is damaged, it'll cost as much or more to replace as the printer.