The light is telling you there is a problem with the engine. Check the oil and coolant to make sure it’s not something simple; if there’s no problem there take it to a Peugeot dealer or a mechanic for a diagnostic check.

If the body repairs are done well and are not clearly visible the affect on a car's value is minimal, but it does depend on how rare the car is. If a car is very rare it will have little affect, but if a car isn't so rare it is likely to have a greater affect. The cars you list aren't terribly old and they are still relatively common in classic terms, so I would be buying the car in the best condition possible. I would be very careful about buying the cars you list, as I reckon you'll be waiting a long time for the values to appreciate substantially.