normally progressive springs come supplied with heavier oil if required and instructions for how much to put in m8.
dunno about Rocket ones yet though, but I will do soon cos I got Hagons on the back but want it a bit stiffer at the front for the twisty roads here in Bonnie Scotland
I think it takes special tools to take the front forks apart, but I dont know this for sure. If it can be done without specialized tools I'll be ordering some pretty soon. Replace the front spings on my VTX 1300, straight forward install, a couple of years ago and thought it was one of the best upgrades I did on the bike.