The rocker covers you cant buy the seals new iirc. Wip the covers off and clean the seals see what the condition is like. Could stick some sealant on with it, tbh they always leak, most people replace them with the plastic rocker covers off the C2 engines.
As for the cam ladders, you need to take the timing belt off. (you could attempt to do it without doing this, but tbh i wouldnt)
Take all of the bolts out the cam ladders, clean all the old sealant off the head and the ladders them selves.
Can get new sealant from halfrauds, put new sealant on and re fit the cam ladders. Might aswell put new camshaft seals on while your at it.
Then you will need to put the timing back on making sure all the timing marks line up of course.