Is it an engine out job to do the shims?
No engine removal required.
On and SP1, you'll have to remove the bolts to lower the oil cooler to gain access to the front valve cover.
On the SP2, you'll have to removed the air guide plate in a similar location.
And the crankcase vent hose to the front valve cover can be annoying to slip off the fitting.
Besides the check and adjustment if needed, the front access makes it a bit difficult the see the cam alignment marks from the side on the front cylinder.
It can be done, just be sure the marks do align properly before torquing down.
A flashlight and small mirror help as well to view from the side.
The cams use spring loaded quieting gears, and you won't be able to fully determine if the cams are aligned until the journal caps are installed and snugged down.
No need to torque until you're sure the marks align as you may have to remove and reposition by a tooth. Then you can torque per service manual specs.
Oh, and the shim thickness marks are at the top of the shim (under the bucket).