First, welcome to the Forum!

The answer to your question will depend greatly upon the stamps themselves. If they are modern (1930's up) stamps, it's generally acceptable to soak them. Look at the cancellations first, though. Unusual cancellations may still make it worthwhile to keep them attached "on piece." Ideally, the entire envelope should have been saved.
For older stamps, it's on an individual basis. If you have some images, it would help to advise you.