Electrode Potential Half Reactions
Yes, you are correct - just flip the sign. As quoted from the venerable UC Davis ChemWiki:


  To determine oxidation electrodes, the reduction equation can simply be flipped and its potential changed from positive to negative (and vice versa).


They give the value for your (forward) reaction as +1.358 V, so for the reaction in question, you'll use -1.358 V.