most of the time on the 620's you don't even need a spring compressor, they will ususally just drop right out with very little help when you get the car jacked all the way up and remove the shocks, but have a spring compressor on hand when you do it just in case, and be really careful when doing it. i would jack the car up but don't remove the shock just yet and wiggle the spring to see if it is really tight or if it moves it around freely, if it moves around pretty easily you should be ok without the compressor, if it is in there pretty tight don't take any chances and use the compressor. but before you do any of this drive it around for at least 2-3 weeks (maybe longer) to let it settle some, the front and rear will generally settle guite a bit usually anywhere from 1/2" to 1", sometimes more sometimes less, but definitely give it some time before you try take it apart again, you could very well end up getting the car too low once it settles