Ill try to post pics if I find a place to host them but usually at the most you can find a monitor for a good deal around 3-4bills.
It's pretty simple if you know how to connect wires power, ground, speakers front left & right and rear left & right and other wires. The input for the AV lines will be located in the back of the monitor/navigation unit. If you buy a DVD/TV/LCD for example.
1. If you put a motorized flip screen without DVD/CD but just a plain monitor just removed the stock connections to your stock deck figure out what the wires mean in the rear of the deck so you can re-wire your new monitor in place. Very very simple. Look in the EverythingCelica. Tech Info it'll show you which wires run to what and will specify what they all mean. It goes the same for a touch screen (watch out for little fingers), combo motorized monitor same ol same ol. Just some companies use different wires when they color-code the connections. Example Toyota!!!! The red for Toyota is not always red. Just make sure you know this and youre good to go.
2. If you're planning on getting just a monitor to flush in with your center console and molding it in. Find a power source to run the monitors power usually 12v source and a ground. The L.C.D Monitor/TV should already be supplied with the proper AV cords so you can run an external unit for viewing a picture on the L.C.D Monitor/TV. Example a Playstation can be your source. Then to get sound get a FM module tuner. This will be your input for the sound to come through the speakers. It works just like a pre-set radio station setting. The FM module will have an AV port for Video (Yellow) and your Red & White (Audio). Plug the PS2 in that module then tune your radio station according to the modules preset where it will pick up audio!
3. Both these setups will usually require you to have a power inverter. A power inverter is just like a wall outlet socket where you can plug things into. Usually they work in you cigarette lighter sockets and plug right in but you can also have steady power if you decide. I recommend just using the cigarette lighter. My trick was go to radio shack get a cigarette lighter socket hide it somewhere where it will be hidden. (example hand rest location). Next connect the power and negative wires plug the inverter socket in that new cigarette lighter location! tada you're set. That's one way if you decide to use your ps2,xbox, separate DVD player, separate head unit, Nintendo 8 bit (right on Isaac!!) etc.
And if you decide on adding more monitors...
4. Hint hint: You will need an AV power amplifier when you split the Video connections so you don't loose picture quality. For those who want that T.V. in the engine bay or wherever you may want to put it.
5. A motorized flip screen L.C.D. 6.5-7 or whatever size you buy will always come with a non viewing safety feature while your vehicle is in motion. It is standard for all monitors that are monitorized in the center console. This prevents the driver from watching T.V. and driving at the same time. Hint hint: if you do plan on buying keep this in mind since many major shops do not disable this feature since it is illegal to. Ruins the fun though doesn't it when you have a T.V. and you can't watch. But! here's a trick you can disable this feature.
Here's how it works it may be different with some monitors that are motorized but the concept is basically the same. What you need to do if located the wire that is connected to disabling the picture. You will figure this out when you connect a monitor but heads up it is usually the wire connected to the parking brake. This wire is located in the back of your monitor and connects to the emergency parking brake to realize a signal. When the e-brake is up the signal is available for viewing on the monitors screen (meaning the car is not in motion since the e-brake is up). So when you put the e-brake down the signal is lost and the monitors picture disappears (meaning the car is in motion). Then you get a blank screen or a caution screen default from factory! This really blows! But you can disable it! With mine all I did was ground it to a good ground location. Ground this wire and tada signal is back!!! And enjoy watching your movies while you drive.
Oh one more thing you may need a new plastic deck kit it's a new mounting plastic bracket that will hold your new deck. The 2000Toyota Echo kit should fit perfect if you can't find a Celica kit. You may need new wiring harness, crimps, electric tape, zip ties, connectors, wires, dremel. But for the most part if you're just doing #1 and just replacing it you can just wire everything and electric tape. I solder all my connections and used crimps for other things it was pretty helpful. If you're creative you can also make one!
Isaac has listed the stereo wiring codes for the GT & GTS heres the link so check it out all the info is already available for ya! Electrical Audio & Video
Hope this helps. For the most part locate the meaning of the wires so youll be more familiar with what youll have to do when you start this project it'll help you throughout your adventure. Good luck!