No DR 500 do not even have to do that, take them in as is and he will strip and re-zinc. Doc, correct wire up and small parts like nipples and alike as they can get lost.
I have used (and use through my business) Ralph (Custom coatings) for years and always does a top job. both silver and gold zinc, did 2 off my 79 red devils a couple of years back and was 70 bucks including all springs, spokes, axles etc anything steel he will do.
The bolt place on Leitchs road is Brisbane Fasteners, good people but not so good on the bike stuff and most (not all but most) of their bolts and nuts are the gold zinc, I have taken to buying up bolts on the net when going cheap (ebay) and when I get a bucket full taken them to Ralph.
Shane