Had my first coil failure last week, the Caddy webs sites predict the first gen coil failure after 75K mi. Go figure I had 76K at the time. Except for the temperature outside I was some what prepared for this occurrence and had ideas where to get the coil if I should need one(or four). To get the car back on the road I picked up a Wells coil pack C1509 from Autozone @ $260
These are the second gen coils which now can be replaced individually instead of having to buy packs of four as the case with the first gen. The price each coil range from $16.00(China) to over $80 from a dealer.
The second gen coils are available individually under part numbers i.e. OEM # 12594176, ACDelco# D596A, SMP# UF564, AirTex/Wells# 5C1613, Duralast# C1556, YJ (China)# 099700-0940, AIP Electronics# U596. On ebay you can get the AIP coils for $26 each. (Note that second gen coils can not be substituted for first gen as the coil plug is different and the mounting bracket is different.)