Vintage is generally accepted to be 25 years old. Most modern machines are made of plastic impregnated with oil. The plastic/oil eventually stops lubricating and you're then expected to throw the machine away and buy a new one.
I have fixed a machine like that, though: A 1980s Janome. A friend sort of tricked me into looking at it. I opened it up and saw the problem (reverse lever stuck). Got the oil out and partner informed me that Janomes should never be lubricated (apparently it's in the manual). I ignored the advice and the machine was working five minutes later.
So it's up to you but I would do it, especially if I were cheap. After that I'd sell it because I hate plastic sewing machines
