Raist,
I am laying out the reality of what occurs in the auto/truck repair industry as to liability. Insurance companies look to minimize losses and the courts determine liability by comparing who made a profit and the ignorance of the consumer on the subject. The customer could be a very competent mechanic but he paid some one to do the repair and the outcome caused a death or injury. As much of the financial responsibility as possible will be laid at the feet of the repair facility and its owner.
When a shop does a repair they assume a large liability. Why should a repair facility do a requested repair or improper repair that places them an even riskier situation? It is one thing to be accused of inspecting a part and making a decision to reuse it. Is is a very different situation to be accused of not inspecting a part, The judge may give you a break if you inspected it and failure occurred. You have a legal argument. You are going to be dead meat if you never inspected the failed part. Especially when brakes are concerned.
If the consumer denies a requested repair then the liability shifts because a repair facility does not have the authority to deny the consumer use of a dangerous vehicle. In some states the repair owner is restricted from telling the consumer how dangerous his decision is. This is because so many facilities use scare tactics to sell repairs.
Randy