O-200
Don't know much specifically about the Socata, but I can tell you a bit about the O-200 Continental.
1300+ hours at 6 or so a year isn't good for them - they develop sticking valves, all kinds of problems and you'll need a top end pretty soon. Use ECI cylinders, set of four installed runs about $5,000 including labor. 1300 hours on the bottom end isn't a problem as long as it is 1300 SMOH and not since TOP overhaul only. Bottom end on an O-200 is generally good for 3K hours, or two top end cycles.
The "ten year" overhaul limit is stated by the lawyers - if the engine is running fine, leave it alone, years don't matter in the real world on this engine.
Fixed pitch prop also doesn't need a "years" service, after some thousand hours they get de-painted, crack checked, reconditioned and re-painted, $300 or so in the US (I am sure it is much more there for the same work.)
Disused airplanes do develop all kinds of strange problems - rusty wheel bearings, stuck gyros, dried out gaskets, hardened brake O-rings, mice and insects taking up residence, I would have to mention that you may actually be getting into a restoration here, which is fine if that is what you want, not so fine if you plan to fly any time soon. (I can relate a story of someone who crawled down the tail cone of a C-150 and came face to face with an occupied wasp nest . . . )
If the price is really, really, really right - and remember you are not allowed to work on this yourself - that's one thing. It really does need to be cheap, because there is very little as expensive as a cheap airplane.
As was asked before - did you marry the first girl you kissed?
Best Regards,
Echo Mike