Spill oil? The filters are sometimes coated in oil, but the filter will be down in your wheel well, no sensors there that I know off. A CAI is a good, cheap first mod. You won't really gain much power (maybe 2~3hp), but it does have a nice sound, and does improve the breathing a bit (which will be important in the future if you add more mods). Before doing any of that though, i'd recommended getting a good tune up on your car though. Replace all filters (air, fuel), oil change (oil filter), new plugs, new wires, check the compression, etc.