Changing dial from RSC

[Koala10]

I am thinking of changing a dial for my Daydate 18206 to another colour. Do I do a one for one change with RSC or still need to top up? How much would the top up be if i still want diamonds? (mine come with diamonds).

If its not a one to one exchange, how much would the dial cost with diamonds? Can I take back the original dial ?

Thank you in advance.