break the tire part way down.. if the tube looks good.. patch it.. if it looks less than good.. repalce it. your tolerance for tire breakdown can be the basis of forming the good / less than good opinion on the tube.
IE.. if you thought breaking the tire down was easy.. and don't mind doing it again if the tube gives out in 2 weeks or 2 months.. then patch it.. save 40$.
If the idea of breaking a tire down is something you want to avoid again till getting new tires ( years? ).. put a NEW tube in.
either way.. make sure the old hole in the tire has a patch ont he inside and the hole-poker removed so it doesn't eat up the new /repaired tube..
( on fronts.. I don't mind patching them.... on rears.. I think real hard on what 'good' looks like. :)