I did a repack for the first time on our 38. Went from the factory flax packing to Goretex as a way to get a drier bilge. Was very nervous about the whole thing worried that I'd get it too tight enough and scorch the shaft or too loose and sink the boat.
Turned out that its not that hard. First go to the web site on Goretex shaft packing. They had excellent step by step instructions.
Biggest thing is DO NOT overtighten after the new packing is in.
Very happy with the Goretex - just a tiny bit of moisture when the shaft turns, shaft stays cool, and best of all, the only water in the bilge is from the air conditioners.