The facts as the Sisters of Charity of Nevers present them: Bernadette died at Saint-Gildard on April 16, 1879 and was buried in the Saint Joseph chapel in the garden; her body was exhumed in 1909 and 1919 during the beatification process and each time, the shrine says, found intact, to the surprise of those present. In 1925, the year of her beatification, it was exhumed a third time and moved to the main chapel. The wax impressions on the face and hands date from that last exhumation, when the darkened skin was judged unsuitable for display; they are why the figure in the reliquary looks as it does.
That is the whole of what can honestly be said. Intact preservation across forty-six years is what the shrine reports, and the Church beatified and canonized her on the basis of her life and miracles, not of her body. Pilgrims should not expect, and this site does not claim, more than that.
Practical details: the Sanctuaire Sainte-Bernadette is at 34 rue Saint-Gildard, about 600 m (0.4 mi) from Nevers station, with reception open 7:00 a.m. to 8:30 p.m. Monday to Saturday and until 7:30 p.m. on Sundays. Mass in French is at 11:30 a.m. Monday to Saturday and 10:00 a.m. on Sunday, with Masses in other languages for groups from May to autumn, evening prayer with the sisters at 7:00 p.m. April to October and 6:30 p.m. in winter, and adoration on Thursdays 1:00 to 2:00 p.m. The existing page on where to see St. Bernadette's body in Nevers covers the train from Paris.