Ive had good luck in the past reworking SMT stuff by removing whatever it was I was taking off with a heatgun by heating up the area enough to flow the solder joints. Obviously you dont want to heat up certain components and also dont want to touch other components in the area when your doing it as they will also be moveable. Once I took off the old chip I cleaned the pads, Applied a small amount of solder to each pad, enough to form a small dome on each one then starting at one pin setting the new chip in place and heating one pin at a time to solder it back into place. Usually I did not need any more solder than what was already on the pad. Worked pretty well for me.. Definetly a down and dirty way to do SMT work if you dont have the right tools. I did however have the use of a microscope when I did it so that made things much easier to see the details.
