First of all, it is illegal to do so. Secondly, the only way is to disconect the speedo sender, which obviously also stops the speedo so you wont know how fast you are travelling, but that will stop the odometer.
yes
If you are talking about the trip odometer push the button in and hold it for a couple seconds. It will reset. If you are talking about the constant odometer, there is no way to stop it, unless you disconnect it from the front left wheel well. By the way, that is illegal.
In the gas tank. I have 2001 Echo.
2001 Toyota Echo doesn't have a timing belt.
http://www.carspace.com/guides/Toyota-Echo-How-to-change-oil
http://pdftown.com/2000-2002-Toyota-Echo-Service-Manual.html
3.5 Liters
see link
timing chain.
32 PSI
go to dealer
i have a 2001 and it gets about 39-42 mpg