i agree with denexo ... Subrip & Maestro are all you need to extract subtitles from vobs and import them to your "new" dvd compilation", but not to put them in the "old" vobs, like i assume you want
btw, i don't remember the name, but there's a prog that can translate subs to your language and, so, you can remux them with Ifoedit...
as said for Denexo, go to doom9 to get more infos ... vcdhelp.com and dvd.box.sk are good places too