it will be cooked when it reaches the internal temperature corresponding to the "done" temperature of whatever meat you are using. From the US food Safety Chart:
Category................................................Food.........................Temperature (°F)
Ground Meat & Meat Mixtures......Beef, Pork, Veal, Lamb.............160
Ground Meat & Meat Mixtures......Turkey, Chicken.......................165
I'd guess that it will take about 45min-75min depending on what size and shape of pan you are using. I personally don't cover my meatloaf with foil but I have a ketchup mixture I spread on the top so while that caramelizes it doesn't really "brown". If you have a "dry" top you may want to consider covering it, but I do find that covering with foil can increase the cooking time somewhat..