I think the lesson to be learned here can cover a couple of different things.
(1) If you pay for a job to be done, go through the job before it is done so as to know what to expect in the end. At the end, check the job from front to back and if you are unhappy with it, solve it at that time instead of months later.
(2) There are less than stellar shops out there, research the shop. If they do not make you feel comfortable, try a different shop.
(3) If you are going to do it yourself and something does happen, you have yourself to blame. Sometimes it is worth it IF you know what you are doing. Sometimes it is best to have the shop do it, provided the shop meets criteria #1 or #2.