Harold:
NM is OK in the garage you describe, no questions, no hassle.
The DW recept as a GFI?.....IF it's a dedicated DW recept it should be a single recept.
The GFI debate came up at a recent NJEIA meeting, the opinion was IF it's a duplex, then GFI based on the opinion tha it could be 'used' for something on the counter. All I see are singles for DW and GDs, and the occasional split 20 amp duplex.
