Sakura would be devastated. She'd immediately use all her medical knowledge to try to find a cure. She might also be angry at herself for not noticing earlier. Kakashi would be very solemn. He'd use all his experience and connections to look for a solution. Shikamaru would start formulating plans to find the cause of Naruto's condition. He'd also try to keep the other friends calm while they search for answers.
Sasuke, when he hears about Naruto's condition, would rush back. He'd feel a sense of guilt for not being around. He'd vow to do whatever it takes to save Naruto. The other Konoha 11 members would also be heartbroken. They'd start looking into old scrolls and legends for a way to reverse Naruto's condition. They'd hold on to hope and encourage Naruto to keep fighting. They'd also make sure that Naruto's last days are filled with love and memories if they can't find a cure in time.
Shikamaru, being the intelligent one, would try to analyze the situation first. He would understand that Naruto isn't himself and would start to plan a way to reverse whatever happened. He might try to gather the other ninja to form a strategy. Kakashi would be deeply disappointed. He has trained Naruto and seen his growth, and this change would be like all his efforts going to waste. He would try to talk to Naruto, using their past experiences to try and break through to the real Naruto inside.
Sakura would probably be very angry at first. She'd likely try to find out the truth immediately and would not rest until she clears Naruto's name. She might use her medical ninjutsu skills to get into the jail if needed.
His other friends like Shikamaru would be in shock. Shikamaru, who is usually calm and collected, would struggle to come to terms with Naruto's death. They would all have to deal with the loss of the village's hero and a great friend, and it would likely change the dynamics of the entire group.
Naruto would probably be very excited and want to immediately start making changes for the better. He has always been about hope and improvement.
I think Naruto's friends would be quite shocked. For the more traditional ninja like Neji (if he were still alive in this fanfic), he would see the gun as an abomination to the ninja way. However, Naruto's closest friends like Kiba would be more open - minded. Kiba might see it as a cool new weapon and want to see what it can do. But overall, they would all be concerned about how Naruto got the gun and what it means for their world of ninjas.
As for Shikamaru, he would probably find the whole situation too troublesome. He might avoid 'female Naruto' at first, but then when he realizes it's really Naruto, he would start to give advice on how to handle the situation in the most efficient way, like how to avoid unwanted attention from other guys.
Sakura might be initially shocked. But being a good friend, she would quickly try to understand what happened to Naruto. She could offer to help him find a way to change back or support him in dealing with the new form. Sasuke, on the other hand, might be more aloof at first. He would see Naruto's transformation as a sign of weakness, but as time passes and Naruto proves his strength in the new form, Sasuke might start to respect him again.
His friends from Team 7, like Kakashi, would feel responsible for Naruto's situation. Kakashi would likely use his resources to find a proper shelter for Naruto. Shikamaru and the others might come together to form a sort of support group for Naruto. They would pool their resources, like money and food, and also try to cheer him up by sharing stories and jokes.
Naruto's friends would react in a very emotional way. Hinata, being his wife, would be devastated. She would stay by his side constantly, taking care of him and their children as best she could while also hoping for a miracle. His friends from the Rookie 9 would all come together. Kiba might bring Akamaru to try and cheer Naruto up, while Shino would be more quiet but still show his support. They would all band together, using their unique skills and abilities, whether it was in combat, medicine, or just emotional support, to try and make Naruto's last days as good as possible.
Sasuke would be more aloof about it. He might not show much interest on the surface, but secretly he'd be observing Naruto's every move. If there was something in the base that could help him in his quest for power, he'd definitely be interested.