By Nicole PensieroFor The InquirerSinger-guitarist John Rzeznik jokes that when the Goo Goo Dolls take to the stage at Philly's Wawa Welcome America! celebration Sunday night, he'll have to don one of his three "rock-star outfits." After all, it's not every day you get to perform in front of a crowd that might be up to 500,000 people."It's wild; we're pretty excited," Rzeznik, 44, said by phone. "I think it's going to be awesome - a huge highlight in our career."And it's a career that's had many highlights, beginning with the Goo Goo Dolls' 1995 breakthrough single, "Name," which arrived after