Depends if you need to have it dovetailed or pinned in. Call XS, they will work with you. Then find a good smith to do the install. I'm putting one on my Colt DS now. Have a non-trit big dot on my 442. I used D&D Gunsmiths in Flint, MI for the SW. I am using a local smith for the Colt DS.
I have a Ruger SP 101 that has an aftermarket Trijicon ramp with dot (pinned front sight). Due to the shallow angle of the ramp and the vial being positioned parallel to the bore, it sits well inside with a channel running to it. The dot is pretty small (0.055 +/-)and being well hidden inside ramp, it's pretty ineffective, IMO. On a gun with an integral front ramp, I would guess this would be a chore. Drilling from the muzzle end through the sight, milling a groove from where the drill blows out of the ramp and starts to wander, and capping the muzzle end of the hole seems like a lot of work for not much reward. Note: I am not a gunsmith. This is how I would approach this problem with my fairly limited tooling and less knowledge of night sight construction. My situation resulted in a dot that is pretty dim and hard to see, unless you have handled the gun with the sight installed and it meets your expectations, I wouldn't bother.
Smith & Wesson did it for me on my Military & Police Model 340. The front sight is a XS Sight Systems 24/7 tritium sight. I liked it so much, I installed a set of XS Sight Systems Big Dot 24/7 tritium sights on my Colt Lightweight Commander.
XS Sight Systems is the way to go in my experience. As already mentioned, they are great guys to deal with and they'll assist you in any way they can.