Defroster Does not work. Blower works, but only blows straight out.

The air, after exiting from the heater, is diverted to the different output ports on the dash by some flaps. In your case the flap controlling the defroster ports is nonresponsive, stuck closed. The only way to find out why is to take out at least the center console and check the flaap itself (it might have been seized in by dirt) , it's lefer (it might be broken) or the control cable (it might be broken or unhooked).
If the fault is with the flap or the lever the entire dash will have to come out to allow for its replacement. In any case this is a big job, that you should leave to a repair shop - no need for a dealer, get the cheapest one you can find.