Yaris 2007 sedan (auto) Transmission fluid change and rear wheel noise

[DevilzMafia]

Hey guys, as I'm new here, I apologize if this is the wrong thread for such a topic. @ Mods do move as necessary.

I bought this Yaris 2007 (auto trans) a year back, have changed the engine oil on good time intervals, but now I have a hitch to change the Automatic Transmission oil. When I checked the dip-stick, it was reddish but with a little noticeable black in it.

My main questions were that:

1) Do I only need to drain the trans fluid through the bolt underneath? or as I've been reading, do I also need to change some oil pan/filter or something like that? If so, could you refer me to the original part no. of that?

2) This second question refers to the second part of the topic. My Yaris makes some quite noticeable noise between 40mph-50mph, which I have a good feeling comes from the rear wheels. The first thing that hit my mind was may be the transmission?, but after putting it at neutral at that speed, the sound is still there, so the second obvious reason came to my mind was 'wheel bearing'.

If anyone has any views, comments, I'd be delighted to hear them, thanks.