Something at least the size of a 737, all the way up to the A380. How are aircraft tires changed for large commercial aircraft?
Are they actually jacked up like with a car?
In general, the jack is put under the axle of the wheel to be changed. Thus the oleo still carries the weight of the airplane and stays at the same extension, and the jack just has to lift the wheel far enough to be able to get it off the axle. Unlike a car, you don't lift the body off the wheel, you lift the wheel off the ground.
Broadly speaking, yes. The jacks are larger and more specialised, but the principle is the same.