Take a look at the Galco Shoulder holsters. They offer vertical and horizontal carry and have off side ammo carries to help balance out the weight. I find them to be very comfortable and adjustable.
Try M Pro 7 bore gel. I'm use it all the time to clean dirty guns at the shop I work at. Just run a dry brush through a couple of times, the put some on the brush run it through a couple of more times making sure you have a nice little coating on the insides. Wait 10-15 minutes and run some...
I run 158 hydra shocks in mine. A word of advice, grip it up as high as possible. I have the web of my had at the very top of the back strap, it keep the gun from being able to rotate in my big hamhocks and cracking the knuckle on my middle finger.
Any holster for an L frame will work. The front sight is no bigger than a traditional blade. But you might want to check out lobo gun leather. He's a forum member and I've had him make several for me and have been nothing but completely satisfied.
Thunder Ranch is a shooting school. And from time to time they talk to manufacturer's and tell them what they think a good fighting pistol is and then the manufacture's will make a model to their specs.
XS makes a front dot front sight for the mountain gun. I've put it on the 2 that I've had and works great, especially with a C&S extreme duty fixed rear sight.
Here's my 625 mtn gun in 45 colt. I did a little work on it. Bobbed the hammer, installed an XS big dot front sight, and C&S extreme duty fixed rear sight.