The maintenance manual that came with the car tells how often (probably every 60-100K).
The capacity of the manual transaxle is: 1.9 liters (2.0 US qts, 1.7 Imp. qts) using API oil grade GL-4 or GL-5, SAE 75W-90 differential oil (the stuff has an awful smell to it). If you don't know how much oil you've got in the transmission, you want to make sure that the level is about 0 - 5 mm (0 - 0.02 in.) from the edge of the filler plug (almost visually full). I wouldn't change the oil as frequently as the author above mentioned, but that's a personal preference thing I suppose.
For a automatic transmission check out this link: http://echodrivers.com/forum/viewtopic.php?f=43&t=13106&hilit=manual+fluid+change For a manual transmission check out this link: http://echodrivers.com/forum/viewtopic.php?f=16&t=10892&hilit=manual+fluid+change http://echodrivers.com/forum/viewtopic.php?f=16&t=865&hilit=+manual+fluid+change - the link above has pics of the different bolts to loosten.
One of the nice features of the Echo is that it has a transmission fluid filter. This means you may never need to change the transmission fluid (it is not listed at all in the owner's manual scheduled maintenance). If you feel that it really does need it because you have not driven under normal conditions, you can find details on how to do it, here: http://groups.msn.com/Sorensonbrian/atfchange.msnw
For automatics, there is no manufacturer defined change interval. If you drive in dirty conditions a lot, you might want to change it every 80k miles. Under normal conditions you may not want to ever change it. There are echo's on the road with 400,000 miles that have never had a transmission fluid change.
Transmission fluid will last roughly 70,000-80,000 miles so anywhere in there.
manual recommends Dot 3.
there are no 2000 yaris that would be an echo
Yes. The fluid should look clean and pink.
Check the fluid.
In any automatic transmission the fluid should be changed at the interval specified by the manufacturer. You should have the transmission oil filter replaced also at this time. Many shops will just suck out the old fluid and replace it with new without replacing the oil filter.
Replacing a transmission is not a do-it-yourself type of job, but I'm sure if you had the time, a shop manual, and a lot of patience, it could be done. A lift would also be nice. Good luck. Personally I would take it to a transmission shop.
One of the nice features of the Echo is that it has a transmission fluid filter. This means you may never need to change the transmission fluid (it is not listed at all in the owner's manual scheduled maintenance). If you feel that it really does need it because you have not driven under normal conditions, you can find details on how to do it, here: http://groups.msn.com/Sorensonbrian/atfchange.msnw You can drain the fluid from transmission pan, but you won't be able to all of the fluid (as there's quite a bit still in the torque converter you won't be able to get from pulling the plug in the pan). Perhaps the best reason to have a shop purge the fluid is that the pan will expand and contract (the transmission oil does get hot). This may cause the pan to not seat properly, and allow for potential leaks along the gasket seal (it's entirely possible, but not likely...). Furthermore, I'd rather pay the mechanic $100 to get oily and messy, and have the burden of having the workmanship be done correctly on their shoulders. You should have the automatic transmission fluid purged and replaced every 60,000 miles or 97,000 Kilometers (depending on your driving habits). You can check the color of the transmission fluid, and if it's becoming a very dark red hue (almost black in color) you should seriously consider getting the fluid changed very soon. It might cost $100 US Dollars to do the job, but that's far less than having to replace the transmission for not performing routine preventive care.