If the C&P is available for your dates online, then change it. If not, it is doubtful you will be able to convert a points award stay to a C&P. Of course there is no harm in calling and asking.

It has been noted that Golds should not expect too much at the Sheraton HKG. If you end up getting a standard harbor view room as an upgrade from a standard garden view, that would be great. Don't expect too much and maybe you'll be surprised!

I have an upcoming stay (on C&P) and emailed the hotel direct to ask about using points or $$$ for an upgrade. I recommend doing the same - they sent me a few options to choose from.

Enjoy HKG!