Thermoelectric Cooler with Arduino?

I know I need a thermoelectric cooler and a n-channel MOSFET but do I also need a heat sink? I'm going to use it to heat stuff up to its limits 180•C and to do this do I need a heat sink? It's going to be in an enclosure so they purpose is to act like an oven.

What are you attempting to do?

AFAIK, thermoelectric devices move heat energy around (as do other devices that act as a heat pump). If you want something cold, the other side will become hot and if you want something hot, the other side will become cold. Energy is not actually removed, just moved. A heat sink may be required to dissipate the heat as the device can only have a certain temperature differential between hot and cold sides. Putting heat sinks on one or both sides would allow for faster pumping of the heat energy.

Max Operating Temp: 180?
Min Operating Temp: -50?

Learn about TECs (Tom's Wiki)
Learn about thermoelectric effect (Wikipedia)
Example Arduino code to control a MOSFET for power

/*
 SparkFun Electronics 2010
 Nathan Seidle
 
 This code is public domain.
 
 Peltier ran at 3.6A @ 11.0V = 39.6W!
 
 The thermo-electric cooler (or Peltier) works well well with a computer power supply for power, a computer 
 CPU heat sink for cooling and a N-Channel MOSFET to control the power. The Peltier is going to use a ton 
 of juice. In this case, I  measured 3.6 amps at 11 volts! I had to attach the hot side of the Peltier 
 to a large computer CPU heat sink but it worked so well that the cold side was so cold I could not keep 
 my finger on the device.
 
 Because I was so scared of pumping 40 watts into a device, I used this program to slowly ramp
 up the power flowing through the MOSFET. Press 'a' to increase power, 'z' to step down.
 
 */

int peltier = 11; //The N-Channel MOSFET is on digital pin 11
int power = 0; //Power level fro 0 to 99%
int peltier_level = map(power, 0, 99, 0, 255); //This is a value from 0 to 255 that actually controls the MOSFET

void setup(){
  Serial.begin(9600);

  //pinMode(peltier, OUTPUT);
}

void loop(){
  char option;

  if(Serial.available() > 0)
  {
    option = Serial.read();
    if(option == 'a') 
      power += 5;
    else if(option == 'z')
      power -= 5;

    if(power > 99) power = 99;
    if(power < 0) power = 0;

    peltier_level = map(power, 0, 99, 0, 255);
  }

  Serial.print("Power=");
  Serial.print(power);
  Serial.print(" PLevel=");
  Serial.println(peltier_level);

  analogWrite(peltier, peltier_level); //Write this new value out to the port

}