Have second root canal or pull?

Hi..I have a root canal that went bad on me, and I have no dental insurance (employer cancelled ours to save $ last year) I keep hearing these stories of people having had a second root canal that's gone bad, and then they're out all that $, and as it is they say it will be $1350 (all of my savings) plus possibly another $900 for another crown if they can't save the old one..moreover I have another tooth that's lost it's filling and 1/2 the tooth, and I was planning having that one fixed until this other tooth went bad..so I'm trying to decide (while in lots of pain) whether or not to have it repaired or pulled..how concerned should I be that the second root canal won't take? Also, if I do have it pulled, how much would a typical molar implant be?
-Laura