The GP and Super Redhawk are very similar to the inside of a SP101. There is a how to do it with some info by Kevin Wilson at:
http://www.sp101trigger.com/index.html
And another:
http://gunner777.wordpress.com/2008/08/24/ruger-gp100sp101book-of-knowledge/
Many people to get an even better trigger and minimize drag on the frame by the hammer use shims offered by:
http://www.michigancenteroutdoors.com/site_map.html
Sometimes firing pin protrusion can be a problem, notably on Redhawks. Here is an article dealing with that:
http://www.thesixgunjournal.net/dialing-in-a-fixed-sight-ruger-da-the-repatriated-ruger-gp-100/
Also, Hamilton Bowen offers and extended firing pin for the Redhawk which also works in the GP100.
Past that, as with S&W, some have delved into lightening the hammer.
Wolff gunsprings offers replacement action springs and spring kits for the guns. In times past Bullseye in Michigan also made kits. Bill Wilson also offers a spring kit for the GP.
The Redhawk differs from other Ruger double actions in that it only has one spring for the hammer and trigger return. Because of this it is a bit hard to reduce the double action
extremely low and get reliable ignition.