Vertical direction (take up as +ve): Fnet = 500 + 300 cos(45) - 1000 = -287.9 N.

Horizontal direction (take right as +ve): Fnet = 300 sin(45) = 212.1 N.

Form a right-triangle from these two Fnet's - hypotenuse is overall net force. Use Pythagoras to get magnitude. use trigonometry to get direction (measured from vertical, say).