from everything I've read on this forum, there are several hours of labor for the vcg, so probably not a cheap preventive maintenance project.
there is a DIY on the site for eccentric shaft sensor that also describes DIY for the vcg:
also read on the forum that some of our cars will leak if left sitting long enough, with the slant in the engine. This may have been the case for me as I was showing some signs of leaks from vcg but no real loss of oil, after my car sat for two weeks. Wiped off the oil, hasn't come back.