When I overhauled my Seville I replaced the regulator. I bought two, and still have one. Contact me if you are interested. Whatever price you can get it at, I will sell to you cheaper :-) I dont think they fail often, but replacing every 40 years or so is probably a good idea.
Great idea on replacing the seals. A REAL pain though. Thing is, the whole fuel rail bends. If I remember correctly, I placed the injectors and the fuel rail back first, then connected the other fuel lines. Definitely an easier job if I had help. When you press down on one side, the other side lifts up and the injectors lift out.
As far as releasing the pressure. The book says to release the pressure through the valve on the fuel rail. Myself, I just disconnected the battery, opened the gas cap, and cut the fuel line at the engine. It will spill some gasoline, but its not going to spray all over. Hold a rag around the hose when you cut it.
While you are at it, Rock Auto has some closeouts on injectors. I replaced all 8 my injectors. If your injectors are all 40 years old, new ones might be a good idea.