I've done it your way and if you are extremely careful you can do it well, without removing the barrel from the receiver.
You're biggest task will be getting the muzzle edges true to the axis of the bore. Just filing the face of the muzzle flat isn't going to cut it.
Once you've gotten the muzzle face as close as you can, you still need to finish crowning he bore. With a lathe, this would be easy. Without a lathe you need to get a bit more creative.
Some good folks, especially smiths are already cringing.
Get a round head cap screw with the head about twice the diameter of your bore. Brass is preferred but steel works as well. Chuck it up in a drill and smear a large dollop of valve grinding compound over the round top.
Take the muzzle and press it lightly but firmly against the coated head, while it's rotating. Carefully change the angle of approach, while pressing the muzzle against the rotating screw head.
It won't take very much effort to grind away the muzzle so that you have an even crown on it. Be careful.
As for your front sight, I suppose you want a blade sight of some sort???
First you will have to acquire a sight. Likely you will ruin the existing sight taking it off, unless it's soldered in place, then it should come off easily with heat.
I will leave the rest to your imagination, with just one more hint. I've used a Dremel with cut off discs to CAREFULLY CUT OUT A channel for the underside of an aftermarket sight.
Dovetail types are unsightly with revolvers but they will work and can be cut with triangular files. AGAIN, BE CAREFUL and keep your patience in check. Don't try to rush anything.