When you put the new gasket back on, be sure to use some Toyota FIPG or some other sensor-safe RTV / Liquid Gasket at the points given in step 7 of
http://www.camrystuff.com/manuals/Ge...hanical_I4.pdf page 57. Those semi-plugs and sharp corners tend to leak out over time unless they get a dab of liquid seal. Oh, BTW, make sure that the valve cover and head surfaces are spankin' clean before you start putting new stuff in there. I like to use a rag dipped in acetone, followed by a Q-tip dipped in acetone for the final clean. Other folks just use paint thinner. Whatever you use, get it clean first, otherwise that gasket is probably just going to leak out again.
BTW, those nuts are 30mm, if you're planning on torqueing them down per spec (spec in the manual I just referenced above). If you're feeling lucky, then a channel lock or adjustable wrench can be used.