Gauges malfunctioning

I recently took my 1997 automatic Ford Escort LX, 52000 Kms, in to correct a problem with my speedometer. At about 80 Kms per hour the speedometer would start to leap erratically and then stop altogether. At the same time the car would begin to surge as if it were not getting enough gas. The “service engine soon” light eventually went on. A scan test diagnosed the problem as the Trans Speed Sensor. The mechanics had a very difficult time removing the old sensor but it was finally replaced with the new sensor. But now both the temperature gauge and the gas gauge are not functioning, both were working fine before I took the car in. Even when the car is not running the temp gauge is stuck at high and the gas gauge is stuck at half full. In an attempt to correct the temp gauge problem, the mechanics replaced both temp sensors, the instrument cluster in the dash, inspected the wiring and tried running a wire direct from the temp sensor to the gauge. (They hadn’t noticed that the gas gauge was also stuck so they did not try to correct that problem). They were unable to find the problem with the temp gauge and have suggested that I go to a Ford dealer. Before doing so I would like to know what to expect and/or what to suggest. Can you help?