How can an engine turn over but sound like a battery problem?
Please try again and tell us what is happening.
Does the starter crank the engine?
If so, does the engine seem to crank at normal cranking speed, or does it seem noticably faster or slower?
If the engine cranks, do you have spark? To check, pull a plug wire off a spark plug and have someone crank the engine while you have a screwdriver stuck in the plug wire boot making contact with the matal part and holding part of the screwdriver about 1/2" away from a metal part of the engine. Don't hold the screwdriver by the metal part. You should see spark jump to ground as the engine is cranked.
If the engine cranks, do you have fuel? Check the fuel shut off switch and make sure it has not been triped. See your owner's manual for it's location. Someone could have hit the car in the parking lot and tripped the fuel cut off switch with no noticable evidence. Pull the cap off the fuel pressure port on the fuel rail and depress the Schreider valve (looks almost like a tire valve) and see if the fuel was under pressure. You should get a small spurt of fuel.
If the engine cranked very fast, you may have flooded the engine and washed out the rings. You can often overcome this by holding the throttle wide open while cranking to clear the cylinders of excess fuel.
Even if the engine cranks at normal speed and you suspect that the engine is flooded (perhaps from a strong fuel smell from the exhaust while cranking) it might be flooded and respond to holding the throttle wide open while cranking.
When replacing the plugs, did you need to move the coil pack out of the way? If so, did you get the primary wires properly plugged back in or did the connector drift loose.
If none of these things helped, try giving us some additional information so we can try to help.
