Hi-I have a 2010 Mazda6 3.7L with 65000 miles. I have always had some issues with odd transmission behaviors, such as occasional hard shifts, but they are becoming more frequent. I don't have a check-engine light, so no codes are known to be thrown by the ODB-II module.
I am aware that there can be problems with the 3 sensors (ISS, VSS, and OSS), and the failure of one or more can cause these issues. I am considering replacing these, to prevent serious damage from occurring. My thoughts are once these have failed, it may be too late.
I have the Haynes manual, but all it says is that these sensors should not be replaced at home ("Note:
The speed sensors on the 6-speed automatic transaxle are integral components of the transaxle assembly and cannot be replaced at home."). It only marginally describes their location, gives no part numbers, and only scant details on replacement steps (which seem really simple, even to a non-mechanic). Are these located in a difficult location to reach, or is wire routing tricky? Do they require a Mazda 3-prong widgit to replace them?
Does anyone have experience replacing these sensors? Is this something I really need to have done at the dealer? If so, does anyone have any idea on the cost of parts and labor?

Thank you!