Usually the factory warranty, right from GM is the best bet for insuring that you get all the repairs done that it specifies. I believe its called the GM Protection Plan. With this car, its worth getting one from GM so that if you need say an Oil cooler in the future, your going to a GM shop that knows best about your car.
Repairs on this car are very expensive, even if its a small item.
You could go with a third party warranty company but your taking a big risk if you do, but sometimes it can turn out for the good. I wouldnt do it for this car, if it were me.
Heres some things people have discussed about this issue, keep in mind that most Cadillacs cost just as much to replace items on ours as it does theirs.
http://www.cadillacforums.com/forums...ad.php?t=13905 (Thinking about a extended warranty) http://www.cadillacforums.com/forums...ead.php?t=3955 (Extended Warranty?)
You can search the fourms if you want, for more threads related to warranty things.