Hi!
My guess is a bad contact between the cable of the upper screen and the main board or a damaged cable. The DS tends to crash when the displays are not connected properly or if they are damaged.
In the first case, just tear the console open using [guide|4784|this guide and reconnect the ribbon cable] of the upper LCD. Otherwise it’s best to replace the upper screen, you can find them for quite cheap on [https://amzn.to/2AtW9o2|Amazon] or eBay. We have a guide for that [guide|4800|here.]
As for the touchscreen, we have a guide for that as well [guide|4786|here], you can only replace the digitizer layer (this layer is effectively glued to the actual LCD panel and its function is to register touches). The glue is easy to remove and [https://amzn.to/2RsDMJO|replacement parts] come with their own glue (as far as I know).