lowering springs!

The Hotchkis springs are much preferable. Ride quality is not too bad and no sag. Nothing really has to be changed with the stock wheels. You will get negative camber front/rear. The rear camber goes out too far negative for the factory adjustment eliptical bolt so you would have to order the adjustable rear camber plates (arms). These aren't cheap. If you don't care about uneven tire wear, then some negative camber in your setup might benefit you on the road course.

As for the front, the negative camber on my car with the OEM wheel worked out to be negative one degree which is perfect. There are eliptical bolts that can be had for about $25 that allow negative adjustment. Also, Toyota makes assorted bolts with varying degrees of positive and negative camber rates to help Dealerships accomplish setting road worn cars back to factory specs.

Note: When changing the springs, the spring perches and upper mounts are oriented on the strut a specific way. Pay close attention during disassembly/reassembly. You should do one side at a time in order to have a stock reference to work from. Just remember that it is the reverse.

Don't forget that you will need a full alignment done afterwards.

As for cost, it is going to be up to who does the work. The Dealership will charge and arm and a leg but will do the best job unless there is a reputable tuner shop in your area to go to.