how can i fix my 2000 jimmy?

the heater is not blowing hot air i check both hoses and the coolant and it is fine. if it is something in the controls will it be hard to fix am i going to have to take the entire dash off and pull the engine in order to fix it. i am looking at buy this car i dont own it yet it is a 2000 jimmy with 105 in milage and is in awesome condition, air blows really cold and is leather and everything. flaw: the heater. i can buy it for 3700 as is. is it worth buying and fixing or too much trouble.