iMac G5 + Garaband, a whole bunch of questions Options

[Premonition]

Hi
I just bought an imac G5. I am still very much used to windows. And there i had a lot of awesome software that i had painstakingly taken months to master. Its all gone now....

To my surpirse i saw a program called garageband in my comp. And seeing the Demos that came, i was pretty happy with the sound of the programmed drums.

My question is....
- How to program drums? My songs usually go in a lot of time signatures and tempo shifts. Does garage band suppot all this?
There seems to be one way that i figured out....but honestly ihop ethis is not the only way to program drums.
What i did was....press the record button...and then keep clicking keys on the on-screen piano....and then go to the edit mode and reorganisee the notes, cos i invariably played them all wrong.

now seriously, there should be a way to program drums by directly pressing the corresponding notes in the edit mode, as in cackewalk home studio pro.
Can someone please tell me whether i can program drums like this? Cos the method i am using is terrible, and most time consuming.

Besides, what i used to do earlier with windows as my os was, create all the drum lines, using a wav trigger software like leaf drums and then arrange them in tracks in cooleditpro, and then record the guitars etc etc etc. This way when theres a change in time signature, all i have to do is create a separate wav fole for that signature and place it sequentially in cool edit.

Can garage band fulfill all these requirements? If not? what additiional software "multitracking" like cooledit should i use here?

If cool edit has Mac support, can someone who knows please gove me a link??

Thanks!!
I hope i made a right decision purchasing the Mac G5 as i herad its much much better than others for recording purposes.