Short answer: MIM Fender are great Basses and the new ones are built more consistently.
Long: I have had my '97 MIM Jazz since my mother bought it on a pawn shop in Mexico as a gift for me on 2009 for about 250 Euros. It helped me get out of a long lasting depression.
The neck was warped, but usable and since then it has got new electronics (60's pickups, fender concentric pots) and a new china neck. The new neck was not great and I'm buying a new fretless one soon.
I agree with david, as long as you get a healthy neck, you are good. I recorded our band's demo with it in its ORIGINAL state and it was a great sounding Bass, beside its 15 years.
To be clear, it didn't "need" to be upgraded, It just sounded fine as it was.
The only original thing left is the body. That body I love, the sunburst finish has been battered, but it is a one pice body, not two or three woods glued together. Also it still has sentimental value to me, so I'm keeping it.