Earlier this month I said you should hang on to your Honor/Justice gear and stockpile your Honor/Justice/Conquest/Valor points, if you did that, your hoarder ways are about to pay off. Patch 5.1 introduces a system to upgrade your gear. Any item over ilvl 458 (with the exception of the Patch 5.1 rep obtained gear) can be upgraded up 8 item levels for 1500 justice/honor points (if blue) or two increments of 750 Conquest/Valor points (if epic). And yes, you can upgrade your DMC trinkets.
The NPCs you want to talk to are located either in the new MoP hubs or Orgrimmar/Stormwind. They are Ethereals located next to the transmog/reforge/void storage guys.