Nissan Repair: coil packs, spark plugs, coils

Question
my car was shuttering when idling, almost dying. the SES light was flashing and engine was shaking. i took it to the shop and they serviced the fuel injector, changed the oil and replaced spark plugs. This didn't help now they are saying the coils packs need to be replace and it going to cost 900 for parts only. Does this sounds right? I know nothing about cars and think i'm getting hosed. Any help would be great.

Answer
Dana,

Yes, the coils need to be replaced and $900 bucks is within range.  But, me, being cheap I would purchase them from rockauto.com or courtesynissan.com for around $65 a coil and that is less than half price.  Also, it only takes a ten millimeter socket and extension to replace them.