As bumper advised, sights are no problem, with a "tool" if you want Tritium Sights, as driving the on with a Hammer and punch, will normally crack the vials holding the tritium gas. Then they "die"!
Pistols without accessory rails, are my preferred carry, as less to possibly snag clothing.
What "bolt on" accessory rails, that were available 30 years ago, normally clamped to the Trigger Guard, and caused more damage, than providing a usable rail... plus finding a holster, to handle it, was impossible.
If you want a rail, to bolt on bells and whistles, get a model with one on it originally. Don't butcher a Classic!