help with 2002 Ford Focus

I have a 2002 Ford focus w/62,000 miles.  Took it to Ford for service twice now and twice charged for diagnostic costs.  At first they said "Tech found nothing wrong."  Today I'm told, "you need spark plugs, spark plug wires, fuel injectors serviced, and a new fuel filter."  I have a extended service plan but Fords estimate, $500.00!   What gives?  How oftedn do i need to change my spark plugs/wires and do i really need fuel injectors serviced at 62,000 miles?  Can anyone explain?

go to parts store get u set of plugs and wires and fuel filter and do it yourself and to heck with extended warranty thats a waste of money