i don't see how you can do the cams w/o taking the belt off and putting it
back on. at that point, the labor cost is dominant and you're crazy not to
do the whole shooting match all at once.
Actually you can. That's how you are supposed to do a valve adjustment
without messing about with the timing belt. The cam pulley and the cam
are press fit together (well that and a big 19mm head bolt.) Remove the
bolt, and press the cam out with the factory cam tool or a harmonic
balancer puller, and the cam pulleys just stay put.