5W-30 should work fine. It's what I've been using.
Should be on the back of the headlight.
Mitsubishi uses metric system.
With proper care, a 1998 Mitsubishi Eclipse should be a viable vehicle for at least 150,000 miles or more. Modern engines and drive trains are especially and comparatively long lasting.
In the fuel tank.
No they are not.
in the fuse box
Yes they will, the bolt patterns are 5x114.3. You could even fit Evo wheels if you wanted to.
No the engine in the 98 mitsubishi eclipse spyder gs is a mitsubishi 4g64 while the engine in the 96 rs is a chrysler 420a engine.
try google
4,3 liter
Yes
in the steering column.