Thank you. So the good news is that apparently there is no way that transmission fluid can get into the cooling system because they are totally independent. This is a great relieve because I had an old Ford (yea i know) that had a radiator that was used for both oil and water... of course they were separate systems but all within the same radiator... and what ended up happening is the inside system for the transmission started to leak badly and the transmission ended up being destroyed because of insufficient cooling.
Now that I have a better picture or what needs to be done, I will be replacing the coolant tank. Fortunately, I did confirm that it is what's leaking, which again is good news because it seems quite simple.
And after consideration, I will be getting the BMW OEM part from the dealer which actually is almost double the price but I can't risk any damage to the engine.
As far as the water pump, I'm intrigued as well. I'd like to replace it with a new one, and also to replace the hoses, etc but I need to do a little more research. I think taking the mechanical fan will be a pain, a minor one I reckon but I'll definitely want to get an idea of taking that part off. Fortunately, it seems that after the mechanical fan is off, it's an easy process.
Now, as I said I just got the car and thought about the transmission but I keep reading that it's "lifetime tested" and there is no need to do anything to it.... of course, that's really unpersuasive, cars need maintenance, simple as that. But when I called the BMW dealer, they refused to do it and said tranny would break. I'll prob leave that as is for now, tranny works fine even at 100K and I'll really hate to get the fluid switch and have it slip, etc.