is it possible to easily replace the subtitles on a dvd i have with the ones stored inside a set of idx/sub-files i have? (i already made an image of the disc which i can edit)

the video can stay intact, the audio can stay intact.... and there's enough room on the dvd for the subs.... what's the easiest way of doing this while keeping the subtitle layout/font (in the idx/sub files) intact? thanks in advance!