welll
The fuel Baffle is what picks up the gas level.
take it out and slide it side / side so the float goes up / down. 
if it's busted it wont work, some people opt to fix them (google sea-doo fuel baffle fix) I personally just slapped a new one in there (I had same issue w/my 98 GTX and 02 XP).
As for the light, fill the oil tank. if it's full, then replace the sensor. the light is just a light, if u unplug the sensor it comes on...
I think i have an oil sensor from a '01 GTX, they may be the same, I could let it go for $30.00 free shipping to US 48 main.
let me know if you need it, I'll get a pic, make sure it's the right one.
I have an '02 XP, getting to the fuel baffle is... FUN 
I removed the plastic under the rear of the seat, got the shock boot off, then removed the 1 big bolt holding the shock to the hull, then, open the front, and u can swing the seat fully vertical, pop the rubber circle off, and get to the baffle, which sits at a 45 degree slant in the tank...
I marked all the hoses with small colored zip ties. (same color on baffle and hose)
BE SURE TO POP THE GAS CAP AND VENT THE TANK FIRST, BEFORE REMOVING ANY HOSES. Else you will shoot gasoline 2 feet vertically in your face (don't ask how I know).
I should have taken pictures, but hey; i was busy working... good luck.