Just go for it, if you want to. It doesn't sound like you're looking for advice, but affirmation. Although if it's in as nice condition as you say, I don't know why you'd want to powdercoat it. Never heard of issues with Panasonic frames, but I haven't heard of big issues with any of the higher-quality Japanese bicycle makers in the 1980's (Miyata, Bridgestone, Lotus, Nishiki, etc.). I wouldn't have any issue with servicing the bike and hitting the road if it's in the condition you say it is.

If you are nervous, then why not just re-tape, do a hub and headset service, put on some new tires, and ride it as is for a while? Then after a few months, you can give it a total makeover.