ABC News' Sabina Ghebremedhin and Amanda Keegan report:

He's one of Hollywood's most doting dads, and even at age 41, the only woman in Larry Birkhead's life is his daughter with the late Anna Nicole Smith, 7-year-old Dannielynn.

So when the show "Celebrity Wife Swap" called Birkhead, expressing interest in featuring him on the program, there was just one issue.

"I was like, 'Look, you guys know I'm not married,' and they are like, 'Does anybody help you out with your daughter?' And I said, 'Yeah, my sister,'" Birkhead told ABC News. "They said, 'We can send your sister and exchange her for somebody's wife or fiancée or girlfriend.' So I said, 'OK, where do I sign up?' and I was packing. I think I actually packed her bags."

Larry Birkhead Reveals Life With Dannielynn After Anna Nicole Smith's Death

The show, airing tonight on ABC, offers an intimate glimpse inside Birkhead and Dannielynn's home in Louisville, Kentucky, as three-time Indianapolis 500 winner Helio Castroneves' girlfriend, Adriana Henao, takes on the role of wife and mom. Meanwhile, Birkhead's sister, Angela Birkhead-Heuser, goes to live with the Castroneves' in Fort Lauderdale, Florida.

"I'm both parents to Dannielynn, so it is hard to flip the switch. I don't have the good cop-bad cop type of thing, so I'm both cops," Birkhead said. "I said the word, 'substitute mom' or 'a wife' to come in, and she [Dannielynn] just immediately lit up and was like, 'Really? Really?'"

Dannielynn's mother, Anna Nicole Smith, died when the girl was 5 months old. Three days after Dannielynn was born, her half-brother, Daniel Smith, also suddenly died.

"It is so much for her to understand," Birkhead said of his daughter. "There are pictures of Daniel and her mom and different things. She knows that they are angels in heaven and that is all she can pretty much understand right now."

Anna Nicole Smith's Daughter, Dannielynn, Asks Dad Larry Birkhead 'Why Did Mommy Die?'

Now, Dannielynn, who recently modeled in her own Guess ad campaign, just like Anna Nicole, may inherit much more than her mother's looks. She also stands to inherit close to $50 million from her mother's long-embattled estate, although, Birkhead says, "I don't really pay attention to that."

Instead, he says, "I worry about my financial situation and that the lights are on, and the groceries," because of the case, Birkhead explains, "was one of the major things in her [Anna Nicole's] life that caused her heartache and pain."

And for nearly eight years, Birkhead says he has harbored his own pain, making it hard for him to move on romantically.

"I want to get out there and Dannielynn has been pushing me out the door trying to get me to go on dates now for a couple of years," he said. "I actually sit at home a lot and watch TV and Dannielynn will point to somebody and say, 'Oh, that girl is cute, Dad.'"

Larry Birkhead, Anna Nicole's Ex, Speaks Out

One of those girls in particular was "Dancing With the Stars" professional dancer, Peta Murgatroyd.

"I was watching 'Dancing With the Stars' and I saw there was a girl named Peta," he said, joking, "And I think I just missed her by a couple of days here in New York, too."

But between the day-to-day chaos of being both mom and dad to daughter Dannielynn, Birkhead says he is ready to start a new chapter.

"This 'Wife Swap' show was a good thing to put into perspective, to see that you do need to spend more time for yourself," he said, "and you need to get out there."