The pedestals are just a light hand press fit and will slide off the shaft, you may have to turn them and pull at the same time because of carbon build-up.
The only thing that locates the shaft is the banjo bolt - if you look at it closely you will see a short round extension at the end, this round extension seats into a hole in the rocker shaft to keep the shaft from turning so the oiling holes are in the right position.
Start by pulling the cotter pin from one end and start sliding the washers, springs, and rockers off one by one - make sure you take notes or photos so they all go back in the right order.
If you can feel any wear on the shaft (or better yet check with a mic), then I would replace the shaft - in my experience the bushings and the shaft wear at about the same rate so if yours is at all loose, changing the shaft will probably help improve clearances. Rebushing the rockers together with a new shaft is the best way to go.
One key when reassembling the shaft - install the pedestal with the banjo bolt first and put the banjo bolt in hand tight to make sure it is seated fully into the hole in the shaft (make sure you can't turn the pedestal when the bolt is in). Then assemble the rest of the pieces and install the cotter pins at the ends. Leave the banjo bolt in place until the shaft is tightened down, then remove the bolt and install the banjo fitting & pipe & re-install the banjo bolt.
Install & adjust valves