https://ruger-docs.s3.amazonaws.com/...77-below79.pdf
See page 7. Maybe Brownells for the spring.
You may be able to get some help at the rugerforum.com site, but if I had to do this and was unsure in any way I would get a fairly inexpensive trigger job from an experienced gunsmith.
Last edited by Big Uncle; 04-06-2014 at 11:18 AM.