Changing the sights should be fairly simple with the right tools. The problem is that a sight pusher will probably cost more than what you can pay to have someone do it who knows how.
As for the laser, I recently added a LaserMax rail-mounted laser to my Glock 20, and it seems to be a nice quality item that holds its zero under heavy recoil, and is easy to turn on as you make a proper draw (trigger finger extended along the frame).
If you feel the need to hang even more crap off of it, the laser has its own rail that you can hang a flashlight on, though I don't know where you would ever find a holster to accommodate all that. I had to make my own for the G20.