Took me about 3 hours of my life, but the missus has a nice pink Nintendo DS now.
It was pretty easy to disassemble the DS. Partial because the original grey casing was already broken numerous times. (It had some adventures with gravity over the years as well as the PSP). I mainly used a single sheet of printed text explaining the method of disassembling.
There are not that many seperate components in a DS. The most frustrating things to reassemble were the top screen connector and the wireless antenna. For the rest it was pretty much an exercise of taking a component and putting it back in the new casing.
Both the PSP and the DS can be back in action for years and years.
Next project: Repairing a completely disassembled Nintendo DS lite with a brand new casing and a brand new top screen. This is gonna take a while.