In that case the top of the instrument must be taken off in order to do the repairs. The soundpost is fitted inside the violin just behind the foot of the bridge on the 'E' string side. Its correct placement is critical to giving your instrument the best possible sound and its adjustment should only be done by an expert. If the post falls down, loosen the strings immediately. Then bring the violin in to have the post set up properly.
Strings Always use good quality strings.
Cheap strings can make even a Stradivarius sound terrible. Even if they don't break strings should be replaced after about six months of use, as they lose responsiveness and quality of sound. When you replace a set of strings don't take all of the strings off at once. Replace them one at a time, keeping some tension on the top. The Bow Like the violin, the bow is fragile and must be maintained properly.