There's a lot of questions, so I'll answer at least a few.
Yep, you pretty much said what you need. An igniter, fuel and air filter oil will get you going, along with a fuel bottle so you aren't spilling all over the place. And you'll need 12 AA batteries (4 for the reciever, 8 for the radio) Many of the retailers on ebay include a free starter kit that has all of that except the air filter oil, which you can get at your local hobby shop. Once you have all that you'll just need some patience to get it broken in and tuned. There are tons of videos on youtube describing how to do that.
As long as you aren't crashing, you shouldn't have much trouble with broken parts. Idon't have direct experience with a Tornado (I have a Backdraft 3.5) but once you start crashing you'll need any number of suspension parts. The steel spur gear is an upgrade you probably want up front as that's the weakest point in Redcat's cars. Lots of people upgrade their steering servos but that's not absolutely necessary, especially right away.
The main problem with the clutch seems to be the heat generated by the aluminum clutch shoes deforming the clutch bell, and the weak spring. I upgraded to a Traxxas Revo teflon clutch and haven't had any problems. Upgrading means switching to something other than Redcat, so you won't be able to order at the same time as your car, but you might be able to find it locally. Take the clutch shoes in to your local hobby shop and see if they have anything close. The Traxxas shoes Ihave don't fit quite right but they work fine.
The DSM2.4ghz receivers have a built in failsafe so you shouldn't need to buy one. My neighbor's Earthquake was configured backwards out of the box though (went WOT instead of brake), so you'll want to check that. There are also videos online describing this process.
As long as you're dealing with a new car sold by an official Redcat vendor, the warranty is handled directly by Redcat and you should be fine.