RogueChomp, you actually do not attach a PlusPower anymore. You play and discard it, with the effect of "During this turn, your Pokemon's attacks do 10 more damage to the Active Pokemon (before applying Weakness and Resistance)." And because of that, you can also use Junk Arm to use it twice if you wanted - and the effect would stack.
And, as per the BW rules change, you may play any Item/Supporter/Stadium cards on the first turn (with the limit of 1 Supporter and 1 Stadium per turn).