I have a '00 taco with about 68K on it and the check engine light has come on. The local shop ran the diagnostics and told me I needed to replace the O2 sensor in front of the cat. con. and also recommended a thermostate and gasket be replaced. The price they gave me on the O2 sensor was about $260 US....is this in the ballpark for this or should I shop around? How hard is it to replace at home? I've done thermostats in older Toyotas, are they still as easy nowadays? Is it really necessary to do the O2 sensor? I know they told me it won't pass an emissions test without the check light off. Just looking for some advice....does anyone know a good online parts source TIA