Can stainless steel be plated with gold?
The process mentioned with the copper plating, then nickel, then gold is one option. However, another option is using the Wood's Nickel Strike solution (step 2 in our kit). The steps in the kit are specifically designed to gold plate stainless steel.
PS I doubt very much a jeweler could gold plate an existing Serpent... the tolerants are so perfect as it is that any coating no matter how think would not work.