If you do send in a Three Screw Ruger for the transfer bar instalation, remove all the original internal parts. Ruger says they will return the original parts, but sometimes they get "lost."
Unconverted Three Screw Rugers are far more valuable from the collector's standpoint, and most serious shooters also prefer them.
If you are a novice shooter, you are better off with a New Model, rather than converting a Three Screw Model. Converted guns usually have very rough trigger pulls, also often develop timing problems. I had one Super Blackhawk converted and never had it "right." Also bought two used Blackhawks that had been converted and they never had the right "feel" to them. Was able to un-convert them, but original parts are getting scarce, and expensive.
Unconverted Rugers, like Colts, Ubertis, Virginians, Dakotas, and Abilenes are old time single actions and require careful handling to be safe. If you are willing to learn and practice handling these single actions, there are none better for sporting use.