looking at used cars. need advice on what to check

[n2knee]

hi guys. im looking at a few used vehicles.

1. '03 Lincoln Navigator 5.4 engine. it has about 70k miles. dealer is asking close to $16k. i don't know the used car market for this vehicle, so i'm not sure what to offer the dealer. are there any known issues about the 5.4 engine or any known issues about this particular model year?

2. '05 Lincoln Aviator 4.6 engine. it has about 57k miles. dealer is asking close to $17k. any things that i should look out for?

3. '04 Expedition EB 5.4 engine. it has around 78k miles. asking price is around $15k. again, like my other questions above, what should i look out for?

4. '06 Expedition Limited 5.4 engine. mileage is about 75k and asking price is close to $18k.

5. '04 Ford Explorer EB 4.6. 65k miles and asking price is close to $14k.

i really don't have a preference on which of the above vehicles to buy. i just need a roomy interior that could accommodate extra passengers, a car seat, a stroller, and a few other things to boot especially on long trips.

thanks in advance for your input.