IDG Answers is a community of experts who are passionate about technology. Ask a question or answer one below.
Hmmm, I guess I would say it is harder than a replacing a laptop’s HDD but easier than replacing an iPhone 5 screen. Here is a YouTube video of a later version DSi screen being replaced, so you can see if it looks like something you would like to take on. http://youtu.be/5IqqNFxE-b0
Personally, I would look at getting her a 3DS, the newer verion of the DS that it more powerful and has 3D display. It's costs more than repairing the DS, but it opens up a new library of games while retaining backward compatability. And for anyone that says handheld gaming is dead because of smartphones, just play Animal Crossing: New Leaf or Fire Emblem on the 3DS and weep at the gaming inadequacy of your iPhone or Android.