As a tech blogger, watching drop tests and videos of phones being disassembled and put back together help me with my work. That being said, I find absolutely no reason for a private consumer to try this at home. Especially when it comes to $800+ devices such as the Samsung Galaxy S3.
But, if you want to replace a non-functioning component with your own hands or to take a look around the inside of your device, just for the thrills, the video below provides a perfect guide. The 20 minute video, by YouTube blogger LE55ONS, is a complete step-by-step guide on how to take apart a Galaxy S3, repair/replace non-functioning components as required, and put it all back together. Let's take a look.
It is a very helpful guide and while he makes it look simple enough, I'm assuming he does this professionally as his YouTube channel features over 50 videos of him taking apart and repairing various types of smartphones. Again, do this only if you ABSOLUTELY HAVE TO, and, even if you need to replace anything, I would recommend doing so by dropping the device off at a Samsung service store.