The sports star will appear in a special Sport Relief edition of the comedy on March 21 - and in his determination to perfect his lines woke up on the morning of filming with the script still on his chest.
"The day of filming started off with a slightly sleepless night, going over my script," David, 38, told the Radio Times.
"The thought of being on set with Nicholas (Lyndhurst) and David (Jason) was obviously very nerve-wracking. I woke up that morning with my script on my chest."
He continued, "I've never done anything like this before, especially with two people I'm really in awe of, and have been for many years."
David, who has been pictured on set wearing a baseball hat and glasses, admitted he could now "die a happy man" after landing a guest role in the special Sport Relief edition of the comedy.
"I'm a huge fan of the show. I have been for many years, as far back as I can remember," he said. "Being from the East End of London, it's what I was brought up on."
It was David who approached Jim Sullivan, the son of late Only Fools creator John, about reuniting the Trotter brothers for the first time since a Christmas special in 2003.
"When he first read the script he was a bit surprised to have been given so much dialogue and was nervous, understandably, about having to act alongside David Jason and Nicholas Lyndhurst, but he had no reason to be because his acting and delivery were very good," Jim said, adding that the footballer's 15-year-old son loved the show too.
"It was lovely to meet hims and hear him talk about his favourite episodes and scenes, and how his son Brooklyn is now also a fan."
He told the magazine, "David got in touch through Sport Relief saying he is a big fan of Only Fools And Horses and that he was wondering if there was a possibility of doing something together for the charity's 2014 campaign.
"We were surprised and flattered by this, but a little hesitant to commit at first. Since dad passed away the question of whether we'd be interested in writing any new material for Only Fools has been raised a few times, and we have always said no, our intention being to protect the work, not to attempt adding to it.
"However, with Sport Relief being such a worthy cause, and with the opportunity to help raise a lot of money, things were different this time, and we knew that dad would approve."
The one-off revival of Only Fools and Horses, which ran from 1981 to 2003, sees the wheeler-dealer Trotter brothers take to the streets of Peckham with a ludicrous plan to get rich quick involving superstar David. It will air as part of Sport Relief on Friday March 21.