Test drove the car for the first time. notice from sittting in the back on the right passenger side heard a roaring noise from the tires. Can you tell me what it may be before I purchase the car? Thanks.

It just started when car reached first 100,000 miles

It just happen out of the blue it worked one day and now does not work at all

While driving at different speeds, air blows under the hood causing the hood to bounce but both latches appear to be latched. I've seen that this has been repaired on other vehicles, but I'm unsure if it's been done on mine. I looked up my vin but it wasn't listed as needing the repair.

Fan does not work. Indictor lights not working or any of the controller functions. Fuses good. Swapped relays good.

I need a new engine for my Altima. The dealership quoted $7500 (which I suspect is high) and are working on a quote for a used engine. I have looked into buying an Engine myself and having it installed professionally. Is that a risky way to go? And around how much would labor to install the engine run do you think? Just a ballpark figure. I just want to make sure I'm not getting the runaround for such a big job. Any help would be appreciated! Thank you!

And it makes it hard for the car to stop when I brake the sound went away when I restart the car and came again while driving it again thanks

My car shows no other signs/symptoms pertaining to a P0603 code, other than the fact the code appeared while i was on a long trip after i had disconnected the battery many times while i was installing HID lights. Will the PCM relearn in time my driving habits, or did i really screw something up that needs to be replaced?

AC compressor stopped working. Connected Freon boost and the needle goes high and pegs. Low side of course.
Nissan "Stealership" wants $180 for materials to look for the problem. Knowing that its under warrenty.

Fuse is good on clutch.
Should I replace the Low Pressure Switch?
I am shootin in the dark without any good knowledge of AC units