Regarding the calipers if the rubber boots for the slide pins perish ect, they can let water in which seizes the slide pins.As i had the same problem looked into replacing everything, Think AClex quoted me £60 for all parts.
Part numbers for fronts:
2 x 47715-22070 Pin, Cylinder Slide
2 x 47715-30060 Pin, Cylinder Slide
2 x 47769-50010 Bush, Cylinder Slide
2 x 47775-30070 Bush Dust
how to here,
http://www.lexusownersclub.co.uk/forum/tutorials/article/161-caliper-slide-pin-overhaul-plus-all-models-i-think/