James is the bar keep on Tortuga, the bar next to Scarlet. (you will soon learn his real name is Carver...hope that didn't spoil too much for ya
)
Burried treasure dig spots can be found by aimlessly running around like a chicken with your head cut off...when you step on a spot, a green circle will appear at your feet, press shift to dig. Or, you could do a SEARCH here on the forums for "dig spot locations". I know there's a thread here somewhere....