Shizuka walks to Nobita's house and explains to Doraemon and Nobita that she was eating peanuts and her mom asked her if she had seen her 500,000 yen opal. It turns out that unbeknownst to her mother, the opal Shizuka had mistaken for a peanut and ate. So Nobita & Doraemon use the Suichu Buggy and the Small Light to get into Shizuka's stomach and get the opal out.
They go in the wrong direction and accidentally first get into her nose, leading her to be unable to breathe! But they fix this mistake and go past her teeth, down into her lungs, which again almost causes her to stop breathing! However, it isn't fatal, as Nobita and Doraemon soon get the Suichu Buggy under control and get into her stomach.
While inside the stomach, they see lots of peanuts Shizuka had eaten earlier. They get the opal back and get out of Shizuka's stomach, but they hide behind a wall and play a trick on her, claiming the Suichu Buggy is stuck inside her and she'll have to resort to... you know. Eventually, they reveal themselves and explain they were just playing a joke. Shizuka is not amused as they had her (and to an extent, her mother) worried. As a result of her anger, she accidentally throws her opal at Nobita and he swallows it. Shizuka apologizes to Nobita for throwing the opal on Nobita and Doraemon has to go inside Nobita's body as the episode ends.
In the U.S. English dub, the opal is part of Sue's mom's $500,000 wedding ring.
Also in this version, Shizuka is watching TV while eating the peanuts, which can explain why she accidentally swallowed the opal as she wasn't paying attention. She's watching a Japanese comedy show. (From the sound of it.)
Doraemon and Nobita get into Shizuka's teeth, nose, and lungs; which they didn't in the 1979 version. It is unknown if this occurred in the manga version of the story (the original.)
All in all, the story itself (manga, 1979, 2002, and 2005) shares some similarities to the Teen Titans episode "Crash."