Whatever you decide to do, you won't go wrong with the Power Custom hammer and trigger. Every one that I have (5 now I believe) all break as clean or better than other guns I have done trigger work on.
That square trigger guard is cussed by some and loved by others. Same thing with the Bisley grip. It is something that differs by individual. The second handgun I ever owned was a SBH, and that trigger guard ate me up. I traded the gun. Many years later I found a nice OM Super priced right and I bought it. First shooting session I was ready for that trigger guard to open some skin, but it did not even hit me. I have come to the conclusion that over 25 years of shooting I now use a higher grip than when I was a beginner. I shoot better now than I ever did back then, and I have two Supers and do not find the square Dragoon trigger guard a problem. Another option is different grips. There are several that will "fill in" behind the trigger guard.
Good luck!
Dan