Master Craftsmen are the dwarf in Crow Perch and Hattori in Novigrad's harbour (love that reference, by the way). You'll have to complete their respective quests, though - level 26 or something along those lines.
For your most immediate needs, a journeyman should be sufficient. Journeyman blacksmith can be found in Oxenfurt - just walk along the eastern wall, should stumble upon him easily. The dwarf in Crow Perch should be a journeyman armourer. Aside from him, there's one in Novigrad's Hierarchy Square.
As for the crafting diagrams... The likelihood that you've got something better is fairly slim unless you've found the diagrams for the cat school or griffin school gear. You'll ulitmately just have to scroll though the list of items you can craft to make sure, though.
@Sprite I'm on PC. Thankfully, because that means I can solve the XP bug myself instead of waiting for CDPR to get their act together