The link is a pretty good explanation. web page
I had a link with some good illustrations as well but couldn't find it.

I'd do it myself and if I mess up to bad it's nice to know I can order a replacement. It's not as hard as some make it sound. Just pay close attention and take small amounts of metal off at a time .

These have been discussed before. All that is needed is to file the sear to 90 degrees so that it doesn't shove up against the spring as the trigger is pulled back. You'll have a nice 2.5 pound trigger in 20 minutes. You can also put a short 45 degree bevel on the edge for a cleam break just as a gunsmith will do on a .45 auto trigger if you like. I can do the factory one faster than grinding down the pad where the safety engages on the Timney replacement, as they always leave a bunch of extra metal, which is understandable, it's nice to have an operable safety. Take the stock off, pull the trigger and you'll see the area that needs the angle changed on the trigger.

The drawing on the Ruger trigger adj. is www.centerfirecentral.com/77trigger.html if you want something to guide you. Anyone with a bit of mechanical aptitude can fix one of these, if not have a friend who is do it for you. the worst thing that can happen is you screw it up and have to buy a Timney trigger for it.

Jim Cloward of Lake Stevens, WA adjusted the trigger on my M-77 MkII 35 Whelen to perfection. One point in favor of an aftermarket trigger is that if you ever have to send the gun back to Ruger, you can pull it out and drop the original parts back in. If you don't, Ruger will remove your trigger (or the original parts you modified) and you'll never see them again. You're out the money and your rifle has a trigger like Glock again. It's part of their liability-protection program. Hope this helps, Okie John.