Depends what mods you do to it.
Things like trigger connector, ext mag release, ext slide release should be fine.
Night Sighs can be changed and changed back with no issues as long as the person doing it knows what there doing and does not damage/scratch the slide.
Mods that are more permanent can reduce the general value but it also depends if there is a buyer that wants that kind of mod. Example, removal of finger grooves (professionally or expertly done by none professional) then it should be fine.