"Usually" the tasks associated to drywalling can be brutal on finished things like that. Not just the dust, but sanding, and texturing.
I would suggest you cover the shelf with brown paper, cardboard and plastic, in that order. The brown paper would go from the lower wall over the shelf to the upper wall following the bends at the corners. The cardboard would run to the plate only on the top of the shelf. The plastic would go from the lower to the upper wall following the bends at the corners. The brown paper may be overkill...but I hate cleaning up DW messes and possibly fixing dings which hopefully the cardboard will provided some cushion for the top. When your done DW, take a sharp knife and cut the plastic and brown paper and cover the small gap with trim of some sort.
Good luck to you...post more pictures when you get it completed.
Thanks! I think my plan is the back edge of the shelf and bottom edge of drywall will be hidden with cove molding: