2000 Other Oldsmobile Models engine or starter?

I was driving this van and it died on me, I managed to get it started again but it only went a short wat and died again, now when I try to start it the starter click once and the motor wont turn over, there is no oil in the coolant and no coolant in the oil, new battery and all other elec stuff workd (windows headlights etc.). I can put the van in gear and push it in both forward and reverse, how can I tell if the motor has locked up or if it is a starter or altenator issue, I checked all fused (under dash and under hood), any help would be appreciated. Rusty