How long should I bake a hamburger meatloaf, and at what oven temperature?
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 &amp; Meat Mixtures......Beef, Pork, Veal, Lamb.............160

Ground Meat &amp; 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..