I did my Vectra the other week. I locked the cams together by using a shaped and profiled wedge between the sprockets before taking the belt tension off.
It was only made from wood, but was a snug 'tap on' fit. Clearly not wellied on, that would be stupid and could cause damage / distortion to the sprockets. At the end of the day, I only changed one belt with it and then threw it away. It did have timing marks on the sprocket as well, but they didn't move at all anyway.
Can't say it was difficult to do, so I don't expect the Stilo to be hard either.