Yes, here a several sites where you can go to seek help withthe repair of your harmonic balancer on your Porsche. www.diynetwork.com/diy/en_engine_block/. looks like agood place to begin because of the stpe-by-step repair guide you will find there. The Harmonic Balnacer repair in the second set of directions.
If you need the part www.damron-ikg.com/p4.htm this site has a Harmonic balancer for a Porsche 928s, 1983 as of today.
If you have an Auto Zone parts stroe near you can also get help from them. There is some do it yourself information on their site www.autozone.com. This website discusses the repair, replacement of a harmoic balancer or vibration damper, another name for harmonic balancer.
There are more sites available to you. Enter harmonic balancer/Porsche into a search bar and you will find more help.