All I know is before you remove the old decals, take everything out. The playfield, boards, etc.

You need to gut the machine. There are no shortcuts to re-decaling. The PF, side rails, bolts, head....I mean everything needs to come out. You must then remove the old decals. I have not done a Stern. But on the B/W I did, I used a hair dryer to remove old decals. Then lots of Goo-Gone and then sand. Prime and then decal. I used Windex on one cab and soap/water on the other. I had better success using Windex. When using the "wet" method. (And I strongly recommend wet) you must let it dry for 3 days. If you are only doing one side, that isn't too bad. If you doing the whole machine this is a pain.

There are folks that have done far more than me, but I've decalled two machines. (MB and SS).
Re-decaling is a LOT of work.
Since your machine is really new, you won't have to fill in any divots.
I have a few pics of a MB that I did here:
http://www.thetheos.com/mb1.html
(The above machine is now owned by a fellow Pinsider)