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You can obtain an mp3 and WMA player from for as little as $89. The most important features are the ability to play mp3 and WMA format files burnt on a CD but also from a USB drive (thumb drive or removable hard drive). Another important thing to consider when upgrading your head unit is what aftermarket unit will fit best. Head units come in three sizes - Single DIN, DIN and a half, and Double DIN. If your unit is Single DIN it will likely be compatible with most aftermarket head units. Otherwise you may need a mounting kit for your vehicle. This will allow the car radio wiring to plug into the back of the new radio. These can sometimes be found for $4.99. Make sure that the plug is compatible with your car (check the list on the back of the box). Twist the correct wires together and then solder them (or use wire nuts if you do not have soldering equipment). Cover the exposed wire with electricians tape or heat seal tape. This will likely consist of having to pry away a plastic cover panel on the front of the radio and take out two screws. This will then allow you to slide the radio out of the dash. If you are unsure how your radio comes out, you should consult a service manual for your specific model. This will be easily done once you slide the radio head out of the dash. These plugs go to the back of the radio and can be released by pressing the release tab and pulling out. If the sides of the radio have mounting brackets, remove them from the factory radio. make sure that you mark which one goes to the left of the radio and which one to the right. This will allow you to fit your wiring harness to your new aftermarket stereo head. There is a place on the back of the radio head for a plug. That is where you will plug the adaptor in. Do not forget to plug the antenna wire into the large round hole in the back of the radio head. This will allow you to pick up AM/FM stations. Be sure that you can hear sound through the speakers. See if the radio lights come on. This indicates that power is getting to the radio. Also confirm that the antenna is plugged in properly by tuning to different FM and AM stations. Mount the new radio with the same screws as you took out of the old head unit, unless you had to use a mounting adaptor. Now you have installed your new stereo head unit. For most Toyota models, including Corolla, you will need to use a dash install kit for single or double DIN stereos. This step varies by model, so be sure to consult your service manual if you are unsure about how to proceed.

Summary:
Select the replacement head unit. Get a wiring harness or adaptor. Connect your new radio to the wiring harness. Remove the factory installed radio. Remove the antenna wire from the back of the radio. Remove the wiring harness plugs. Remove any mounting brackets. Plug the wiring harness adaptor into the wiring harness. Plug the other end of the wiring harness adaptor into the radio. Plug in the antenna wire. Test the radio. Slide radio into the head unit slot. Reinstall any panels or pieces of dash that were removed.