Not knowing what the codes are or the meaning of the codes for the transmission I would suggest:
Change the tranny fluid and filter using ATF+4 FLUID ONLY, if anyone tells you that you can use a universal fluid and a additive that the vehicle somewhere else as the incorrect fluid can ruin your tranny very quickly.
As for flushing the tranny that is something I DO NOT recommend. Using a flushing machine for one you do not know what contaminates could be introducted to your vehicle from other vehicles plus it can stir particles in the tranny that are better off left as is. You can change all the fluid by disconnecting a tranny line, if you want to do this let me know and I will explain process as best I can.
Look in the online service manual thread in this forum and look up your vehicle and it should explain the function of the input an output sensors.
When changing fluid and filter I would check the wiring and conncections for the input and output sensors to make sure they are OK and if so install new in and out put sensors before messing with the solenoid pack.
If you are mechanically inclined or know a friend that is capable of doing this work you could save yourself many dollars rather than the stealership. You can get the ATF+4 fluid at walmart for around $4.50 a quart and should take about 5 quarts with normal filter and fluid change or a complete fluid change would take approx. 12 quarts. The sensors are not hard to change. Again look at the online service manual it may show location of sensors.
Hope this helps