The seats are held in by 4 bolts on the floorboard. Remove these and the seat will come out easily. You may need a breaker bar to loosen these bolts. They are on tightly, because they are critical in a crash or rollover.
The battery is a Mt-MX5. This is a Interstate battery part#. fits 1990-2008 Mazda Miata. Go to interstatebattiers.com to find a dealer near you.
Yes you can, but take it to a shopAnswerYou should NEVER, EVER replace a manual transmission a Miata. Learn to drive stick. No exceptions, except amputees. Answer
It would take a lot of work, and gas mileage would be worse, reliability would be worse, but yes, it has been done.
4 quarts
3.8 to 4 quarts of engine oil.
Take off the airbag on the steering wheel, there are 2 wires, remove the black one....I think its the black one, well remove one then see if the light is still on
10w30
You take it out through wheel well On this page you have directions how to do it http://mx5unleashed.com/tech/starter-mx5.html
Definitely take apart the gauges, check and make sure all cables are intact.
The life expectancy of any vehicle depends on how well the owner takes care of it. As the Mazda Miata tends to be an enthusiast's car, the owner may take care of it, and thus it will last longer. My 1990 runs just as good as the day it was made, if not better, because it was taken care of. I fully expect the car to last another 20 years.
Mazda recommends 75w-90 weight oil for the manual transmission, changed at 30,000 mile intervals. See http://www.miata.net/garage/maint.html for more information
There is a problem with the air bag system. Until it is fixed the light will remain on. Take it to a garage for repair.