As mentioned before, the service cost is minimal for the R134 if you do it yourself. It's worth a try! It's really very simple. If it's a high mileage car and it lasted for that long and you re-charge it, hopefully it'll last that long again! There's no real easy way to find leaks in an A/C system. There's a procedure with injecting dye into the system that's sensitive to ultraviolet light. It all depends what you're up for! Most of the above can be had at your local autoparts store.