What is the most effective method to utilize a gear cable repair kit when dealing with a frayed gear cable and are there any potential risks of exacerbating the issue, can a repair kit adequately restore the original functionality of the gear cable or should a new cable be installed instead, what are the key factors to consider when determining whether a repair is feasible, how does the type of fraying, such as the location and severity, impact the decision to use a repair kit, can a repair kit be used in conjunction with other maintenance tasks, such as cable adjustment and lubrication, to optimize gear shifting performance.