A crack in the valve cover will certainly cause you to be lean, but it usually has other issues like idle irregularity and loss of pressure in the fuel system.

Some guys "true up" the bottom of the valve cover on 400 grit sand paper. If you decide to di that make sure the sand paper is on a good flat surface. As for other parts, regulator spring, diaphragm, plunger, and get a spare check valve. The check valve is always a good spare to have in the field box.

Let us know how it turns out.