Thery are difficult to change.
Many guys just put a BB in the line and live with it. It is only there as an emmissions device and only holds the car in 2nd gear delay when it is cold at first start-0ff to aid in rapid cat warm-up You can let the engine warm up a little on cold days and it will not trigger the CE code..I just keep it in low gear selection range when cold for a few moments manually. That does the same.

...but if you do want to change the unit, it can be done . Try the archieves for step procedures.