Transmission

If you do it correctly you won't have any problems at all. I did a fluid and filter change on my wife's car about 3 months ago and still haven't had a problem with it. If need be watch a couple videos on how its done first so your more comfortable when doing it.

Thanks . But I still have a doubts about the filter since they insisted not to changed it.

I would change out the filter as Well if your going to do a fluid change. The filter is not hard or a intimidating task just look how it is placed and watch how you take it out and you will be fine.

if it has not been changed after like 20 thousand miles I wouldn't mess with it even with rip off fluid changes, always problems some dirt or something can and will dislodge and start clogging the tinny grooves which in turn may cause serious issues down the road or even right away. Just a thought :)