I bought a 2000 2.5 Auto GT wagon in March. Points to look out for from my experience.
1. Oil leaks around the engine, lands on the exhaust down pipes and smells. Worst case, creates smoke. Likely culprits, head gaskets, rocker cover gaskets, sump seal, drain plug seal, engine/gearbox seals.
2. Sunroof seals. The steel frame under the rubber gaskets is corroded and affecting the sealing.
3. Stereo and speakers. Had to replace mine, the speaker cones were cracked due to old age. Not a major issue but may give you bargaining leverage.
4. Lower wheel wells close to door sills. There's a little ledge that can accummulate road grime and promote body rust.
Otherwise the usual second hand car nuances.