That's prob not a bad idea get a 2nd opinion if you can get some one (real mechanic) to look at it quickly i case there is something obvious that the apprentices at Nissan can't see then get nissan to fix it and flip them the bill.but sounds like Nissan has just had your car in the car park the whole time you had it there, these hoses you have found yourself should have been picked up I would be blasting them over it!