let the alignment shop do it. the easiest way is to put the shims in with the upper
a arm when you replace it. you can jack up the front off the ground and loosen off the upper a arm bolts and pry the a arm back ,slip in the shims and tighten .do not take the nuts all the way off the bolts.
I will put the existing shims in their original location and hope the alignment is within specs but if not how can i change the shims with the massive spring pressure?