So do you know the code that caused your check engine light to come on??

Usually the oil leak around the the valve covers is not actually from the valve cover gaskets . . . it's from the breather covers. There is no gasket for the breather covers, they are sealed in place with permatex form-a-gasket type sealer. The OEM sealant dries out cracks and fails . . . a very common problem on all Crossfires.

Regarding the throttle body, I've really never heard of a throttle body failing or causing the battery to drain (buy maybe it could happen). If you do end up replacing the throttle body buy a used one. It does NOT have to be programmed but after you install it you could do a throttle reset though . . .

Perform a throttle reset.
1. Turn the key to the on (not start) position, the position just before the starter turns over.
2. Press the gas pedal to the floor with the key in the "on" position.
3. Hold the pedal to the floor for five seconds, then turn the key back to the "off" position (don't remove the key), then release the gas pedal.
4. Don’t remove the Key. Wait 2 mins. for a full alignment.

When you pick up your car I hope you let the stealership know that you will not be coming back there.