The Whiteline kit (kca428) is awesome as it provides caster correction and improves turn in and overall steering feel. But its not the cheapest option.
You need to remove the control arm completely and either cut/press the old bush /sleeve off the arm.
Fitting the OE style bushes would be the most difficult out of the options, as you need to maintain the alignment relative to the arm when you press them on (the rear control arm bush doesn't pivot) its kind of preloaded once its fitted, and can be a little annoying to get the bolts started as the threads are part of the bush. They are also oil filled so if you press them in like a gorilla you can ruin the new bushes.
The urethane bushes are easier to fit as they will pivot
Complete replacement arms are cheap enough from sandwood trading if you want to avoid the hassle ( be aware there are 2 different ball joint taper sizes )