Is this jacket true to size?

No. The listing states it fits large, so size down if you want a regular fit. Treat the labeled size as a starting point and check measurements before buying.

What condition is it in?

Good, with pulled threads noted. Pulled threads are snags where the yarn has been caught and drawn out; they are cosmetic and can usually be eased back with a needle.

A polyester blend. That makes it light and quick-drying but not breathable like cotton or wool, and it offers little warmth on its own.

No. It is a fashion jacket from the 1990s, not a technical shell. It handles a light drizzle at best and needs a proper rain layer in wet weather.

Is a 1990s Dior jacket worth buying?

For label and era collectors, yes. Licensed 1990s Dior outerwear is common and not as rare as couture, so value rests on condition and fit, not investment.