Hey Jersey Paul,
Welcome to the LTG! That's quite a nice deal you got. If you want to retain authenticity, a trusted luthier should be able replace the missing MOP. That is the more difficult route, however. It'll be hard match the aged color of the remaining inlay. The easier method is to just replace the complete overlay a la GoG's post. Post some pics. We like pics, even of ugly stepchildren! Also, I don't know if there were ever any blonde SF IVs in '67, but with Guild, one never knows. My guess is that it probably is a refin. If it is, then you shouldn't feel guilty about your own refin. If you PM/email Hans Moust (username -- hansmoust), he can probably tell you more about it.
Is the amp you bought a 1982 Fender Princeton Reverb II? If it is, you got a
killer deal on a great little amp. These Fenders are sleepers.
Paul Rivera (custom amp builder) designed several models of Fender amps from '81-84. These are all-tube, hand-wired amps that were designed to compete with Mesa Boogies. Off the top of my head, I think they take 7025/12AX7/ECC83 preamp tubes, a 12AT7, and 6V6 power tubes. Supposedly, they are infinitely moddable, and you can "blackface" them with the removal of one capacitor. I've always been intrigued by them, and they're still very affordable, albeit scarce.
Here's a page telling all about them.
Cheers and happy happy!
edit: Okay, so I'm checking out that PRII website, and I see that Fender claims it was Ed Jahns that designed the Princeton Reverb II! Funny that this is the first time I've ever read that. Always heard it was Rivera. Oh well, it's still a great amp! Here's a link to the info:
http://www.geocities.com/princerev2/magazine.html