Aftermarket triggers can often attain safe, low trigger weights that are difficult to attain with modified or adjusted stock triggers. They re-engineer the trigger mechanism to make it specifically designed to safely operate at lower weights. I've never installed a Ruger trigger, but I've used aftermarket triggers from Timney and Sharp Shooter Supply (a Savage specialist). They are not difficult to install, but require careful following of instruction for safe installation and adjustment. They are not simply drop in, in the sense that they have to be carefully adjusted, often in 3 stages, to get the right weight, desired sear engagement and operation of the safety. Sometimes minor fitting is required, wood or trigger guard may need slight clearancing. I hope this helps. Give yourself an hour or two to carefully read the instructions and set the newly installed trigger up properly. I've heard good things as well about the triggers from Rifle Basix, and they make one for Ruger.
Make sure you research the specific one you intend to install, as some have complaints.
I have a Ruger 77 rifle and I contemplated buying an aftermarket trigger for it. Your results may vary, but in the end I modified the original trigger, following the advice of some, and against the advice of others, as it did require modifiying the actual trigger and sear by removal of metal. The profile of the trigger mechanism on the stock Ruger 77 rifle benefits from a change in shape, but removal of metal removes hardened surface that resists wear.
