I remember looking at these quite a few years ago they where and still are incredibly expensive watches I think the watch contains 2 batterys or some of the movement photos I have seen show two and changing requires partial dismantling of the movement in some cases, its is a incredibly complicated movement I would not even think of replacing a battery on one myself so to answer your question take it to a authorised service agent and let them do it these retail at about £15,000 new and £7,000 secondhand why risk it if a battery change is £200.00 I would say money well spent on a watch like this,
Poor video quality but it gives you a idea of the movement