Also, do NOT, I repeat, DO NOT take the easy way out and cut the old bearing and collar off with a torch... it needs to be cut off properly with a cold chisel.
Heat from a torch can re-anneals the metal of the axle itself, and renders it weak at that point. It will gradually work harden from the stress of cornering etc, cracking slightly with the crack gradually getting deeper and deeper, ultimately breaking off and sending the wheel and hub in one direction while the car goes in another.
Someone (a previous owner) torched off the left rear wheel bearing on my wagon years before I got it. I was driving down the highway with my father in law (80 + mph). We took an exit with a sweeping right turn, and just as we came off onto the city street, off came the wheel. No warning. 1 minute earlier and it would have been on the highway, and people likely would have been reading about it in the newspaper obits and seeing the carnage on the TV...
Upon examination it was easy to see where the torch had touched the axle and created stress point, and it had gradually worked its' way through until it was too weak to stand up to the stresses of cornering.