Recently we put our 05 Altima 2.5s in the shop and they found that the oxygen sensor was bad so they replaced that. Got it back to the house and it ran fine for a couple of days then all of a sudden it would not start at all. So we called them up and they were much nicer this time than last. They payed to have it towed and found that the crank position sensor went bad. All of this was covered under warranty so we didn't have to pay a thing.

Recently we put our 05 Altima 2.5s in the shop and they found that the oxygen sensor was bad so they replaced that. Got it back to the house and it ran fine for a couple of days then all of a sudden it would not start at all. So we called them up and they were much nicer this time than last. They payed to have it towed and found that the crank position sensor went bad. All of this was covered under warranty so we didn't have to pay a thing.

Another problem to look out for is the front undercarriage. My aunt has a car like you but she has an SL. Her front undercarriage fell off along with some mild rusting under the rear -near the right wheel- and costed her around $1,500 for parts. THIS WAS NOT COVERED BY WARRANTY.

Just a heads up for future reference. :D