Howdy
Follow this link. When you get to the page click on the button that says Ruger Tech Tips. You will get a list of videos. There is one for disassembly of Ruger single action revolvers and another one for assembly of Ruger single action revolvers. Pay close attention, they are very good. Do everything the guy says, and pay particular attention to the details.
You also have very good disassembly and assembly instructions in the manual that came with your Vaquero. If you don't have a manual, you can download one from the Ruger web site, or you can call Ruger and they will send you one for free.
http://www.ruger.com/resources/videos.html
I have put Wolff springs in bunches of revolvers, Rugers included. Frankly, I don't remember how far you have to take a Ruger apart to change the springs, I have not done it in a long time. But you are best off learning how to take the gun completely apart and how to put it back together again. It will be obvious when you have taken it apart enough to change springs.
When you have removed the grip frame you can remove the mainspring with its strut. Be sure you have pinned the spring in place as shown. Now comes the tricky part. I like to secure the strut in a small vice, and compress the spring with the slightly spread jaws of a needle nosed pliers. Straddle the strut with your pliers to control the spring. A fork can be used to. You need to compress the spring a little bit more so you can remove the pin.
Be VERY CAREFUL when removing the main spring from its strut! Do not get your face in the line of fire! The spring is under a great deal of tension and if it gets loose it could take your eye out! You need to control the spring when the pin is removed, gently relieving the tension with the fork or pliers. Keep your face out of the way!
Putting the new spring on the strut you reverse the process. You have to compress the spring enough so that you can put the keeper pin back in place. Again, be very careful. It is easy to slip and allow the spring to jump free. Keep your face out of the way. Try to do all this in a well lit area. If the spring jumps away it is guaranteed to find the most inaccessible corner of the room, most likely hiding under something.
Follow the rest of the video to reinstall the new spring and strut.
Pay close attention to what the video says about making sure all springs and plungers are properly lined up.
The trigger spring can be replaced when the grip is off. Pay attention to the video about popping the trigger spring in the correct position when reassembling the grip frame.
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Frankly, I have to agree with Flatgate about springs and action jobs. Too many shooters believe that replacing springs is the same as an action job. It is not. An action job will remove extra roughness and friction that is in the action. If this roughness is not removed, the lighter spring may not be able to push the hammer fast enough to fire primers reliably.
I am not going to go into an action job here, but here is one trick you can try. Make sure the gun is unloaded. Cock the hammer. Push hard against the hammer with your thumb while slowly pulling the trigger until the hammer falls. Do this two or three times. Just push hard against the hammer and at the same time pull the trigger very slowly. This will help 'marry' the parts together, removing some tiny imperfections in the fit of the hammer notch and the sear. Just do it two or three times, don't over do it.
Do not try the same trick with a Colt or colt type lockwork, you may break something.
