Q&A

I don't have the maintenance chart for the 2007 Sebring, but if you look at the parts that are actually replaced at the 60k service, that will give you a good idea as to what is most important, as well as an inspection of the brakes, belts, hoses etc.
Your owners manual should have the maintenance chart.

Going with the owner's manual is the best thing that you can do. The manufacturer has recommendations that are specific to your car, so you can ask the dealer to include what the manufacturer recommends and ask for them to justify everything above and beyond that.

The spark plugs in your engine are standard resistor plugs. Your Spark Plugs should be replaced every 30K miles. Spark plug wires should be replaced every 60K.