Agent Sharp,
Yes, heating up the engine to operating temperature is the best way to change the oil. Oil flows better when it is warm. By heating it up and letting it drain for a while you will get more of the oil and some of the sludge out of it when compared to draining the oil on a car with a cold engine. You just have to be careful not to burn yourself on the oil. I wear rubber gloves when I do my oil changes and keep a rag nearby just in case I do get some of the hot oil on myself.
Mike