The P71 was the old name Special Service Crown Vics got from '93-'98. After that they were simply named Police Interceptors. What exactly do you want to know about them? Same power train as a Mustang, they're certainly bigger than a Mustang, with more trunk space to boot.
If you're able to find one, expect it to have a lot of run time on the engine. Don't let lower mileage ones fool you....those baby's have sat and idled longer than most cars have actually driven, but this usually knocks the price down on them quite a bit.
would it be a good vehicle for a daily driver, and what should i look for when i go look at them? how long do they usually last mileage wise?what usually need replaced on them?
Probably the biggest area of concern will be suspension components. They really take a pounding with these cars. If you find one, look at it needing most of the rod ends, ball joints, shocks and possibly bushings replaced. Otherwise, the 4.6L in these cars is every bit as tough and reliable as any and will last a long, long time.
My buddy has a 97, which we swapped a PI intake onto the third day he had it. His stock intake cracked in the summer on the crossover. I threw a spare PI manifold of old design on it, and it cracked this morning. That's all I have to complain about on this car so far. We put a Transgo shift kit in it, and it is AWESOME. I love frame vehicles!