I've never worked on a Ruger SA revolver
The GP-100 is not a single action revolver. Its double action. And you don't have to remove the hammer to replace the hammer spring. To replace the trigger return spring you have to remove the trigger group housing. The disassembly instructions are in the owners manual IIRC. If the OP doesn't have the manuel its free from Ruger. It says so on the barrel.
The OP is talking about the hammer pivot pin that will drop out of the gun when taken apart correctly.
To remove the hammer spring on the ruger single six you have to remove the grip frame. I don't remember on the full size single actions, its been too long since I took one apart.
The OP doesn't sound like someone who is familiar with taking guns apart and should get help before he messes his gun up.