I would have thought that the dealer will perform this upgrade for you, as it only takes a small amount of time (when my BV7-32 was HD upgraded, they had to perform a SW update, which took less than 20 minutes, if I can remember). You could either pay your dealer to visit you or, if you ask nicely, they may send someone round at their convenience.
I'm wondering what is updated in the BS3 4.0 SW update? Anyone know?