Hi Michael!
At this moment I recommend first to try another screen. Just to check if the screen is OK. If it's still having issues, it's motherboard related.
Now first try to replace the DS game card slot if this failed,, then it's for the best to replace the CPU on the motherboard (the 3D engine is in it).
Hopefully it's the screen, this repair is the easiest one and hopefully that will fix it!
[image|3372522]
Please let us know how it goes!