NEED HELP

[Sandra]

I have a 1990 240SX Hatch Back. problem is I'm getting no interior heat. My guess is my heater core is shot. The fan is working for my climate controll. the "in" hose to the heater core is hot but the "out" from the heater core is cold. BLOCKAGE?

Second thing i gotta do is coolant flush it, but i can't find the engine block coolant drainage plug/screw and onw know where it would be or how to get at it?

THANKS FOLKS