Personal opinion ahead:
The N2DSXL is the worst of all DS to disassemble. The upper LCD assembly is held together with a lot of strong adhesive. Easy to damage the very thin LCD which has no metal shield (you know: slim, light...)
Even opening the lower part of the shell is tricky; clicked together. I ripped off the plastic notch of the internal volume slider without even noticing (a part to pay attention to when opening). Did this last year and put it away since... It is a unit I got practically for free (paid only for the Mario Kart 7 license) with damaged upper screen. So I did the disassembly and broke the upper LCD to pieces. Granted, I wasn't careful since it was already busted.
Doing this without damage will require skill, something to carefully heat up the adhesive and a lot of patience.
Again, personal opinion:
I wouldn't open a working N2DSXL.
Good luck and have fun!