You decided to dive in then :biggrin As you've proberbly realised it's easy to make the crank holding tool & yes you can only do one cylinder at a time, don't be tempted to remove that bolt untill it's all back together.
There not much of an Aprilia dealership if they don't keep shims, don't they do any servicing :dunno when I did mine the dealership just let me exchange my shims for ones of the correct size from there selection they keep for servicing.
I found that I had to remove that coolant hose & the round coolant junction "can" to get at the adjusters.