No spark,help!
 

My Saturn sc2,1993,has over 300,000 k on it. Never given me any issues until now. The 2 inner plugs have no fire. Replaced the coil pack and it ran fine for a few days and did the same,no spark. Relaced the coil again and still no spark. Could it be the crank sensor and where is it located and is it hard to replace?