I passed 90k on my car about a month ago. With proper maintenance, you can probably go 200k+. After that I think repair cost would exceed the cost of the vehicle.
I couldn't say between those cars, since I don't know their specs. I'll just say that the Mazda looks nice.
Firstly, it depends if you know how to drive stick. Next, do you want the luxury of being able to drive and potentially (and safely) multitasking? Then, is the price difference between the auto and manual models significant enough to warrant the manual.
1. Lol 90K is nothing depending the type of car. Like Hondas usually last to 300k-350k miles (Which is hella a lot), Lol my sister had a 1989 Honda Civic and it lasted till 450k miles, Lol but I don't know how.
2. 2011 Nissan Sentra
3. Manual makes you a better driver and prevents you from falling asleep while driving.