Heater Only Blowing Hot

[Will Eastman 6]

hey i have currently got the dash pretty much out of my car. The car heater has worked fine but only has one setting, hot. You can turn the nob fine but it doesnt change the heat. I have got to the heater and can now see that the nob turns the leaver fine. So i guess the problem is inside the heater. I dont know what to do now. Should i take it out?? (if so how) should i take the front off or something??(if so how) or should i just replace it? (if so how) haha bet you can tell i dont know how to do much hehe thanks guys