I replated gold parts, mostly tuner buttons, on my Guilds. Most were worn but not pitted. I used a gold plating kit from:
http://www.caswellplating.com/
and it worked very well. Also worked on the guitar case hardware after some cleanup. If you decide to replate, the parts must be polished (I used auto machine glaze compound and a dremel cloth wheel) and degreased with acetone prior to attempting to plate them, otherwise the results are spotty and you will have to redo the job. If parts are visibly pitted, simply replace them because you can't successfully replate corroded parts; The plating either won't stick and/or the pitting will not be hidden by the new metal coating.
From a personal perspective, I am proud of my instruments and I want their appearance to reflect that pride. Since I don't intend to ever sell them, I don't much care about if replating parts will affect resale value.