We'll "pardon your French" ;]
He's wrong on the year, but this is still a great bass, a great way to "get into Guild".
If he means the neck is slightly bowed, so it mine. If it's warped diagonally, like airplane propeller, forget it.
A quick sight down the frets will tell you what you need to know.
You can take some of the bow out with lower tension strings, like Thomastik Infeld Flats, although wound strings are actually lower tension than flats, the TI's are very low tension. I have D'addario Chromes on mine, the relief is perfect.
The relief is there without any strings on in fact, slightly bowed neck. I let it sit with no strings on for about a day, limbered up the truss rod that had probably never been turned, tightened it as much as it would go, 1/2 turn from seated - with nut driver only - to counteract string tension and it come out perfect with strings on.
Get him to reduce his price because it's not a '69, they didn't even exist then, the bowed neck, and the missing screw, and whatever else you notice wrong with it, fret wear, electronics operation, etc.