In order to fix Scrapper, speak to Gondo at the Scrap Shop in the Bazaar. This is also the shop where you upgrade items. He will ask if you need a favor from him. Reply "Yes." Gondo will talk mention ...
Enter the dungeon and have Tri create an entrance to the rift. As soon as you do, you'll see Link run up the ladder ahead of you. Follow him to a sublevel with several wind-cannons. You'll want to use ...
The first stamp card will given the first time you meet the Stamp Guy, at any Stamp Stand throughout Hyrule. If you fill it out with 5 stamps you will be rewarded with 5 containers of fresh milk.