Gentlemen, start your engines! Jessica Simpson performed a pre-race concert and sang the national anthem at the NASCAR Bank of America 500 on Saturday in North Carolina, but before she crooned for car race fans, she spoke to ET about love with NFL beau Tony Romo! The beauty also got a lesson in changing tires at pit crew speed from pro driver Scott Wimmer, and ET caught it all on tape!

Jessica dished about her budding romance with Tony -- and debunked some crazy rumors in the process!

"Tony and I have not gone to Neiman Marcus -- somebody said we bought a ring there," Jessica tells ET about engagement rumors. "I couldn't drag Tony in to Neiman Marcus if I tried."

Jessica also says she is "beyond the moon and stars," adding, "I'm very happy."

Watch Jessica's revealing chat with ET, and then watch her help change a tire!