I'm new to Android... few questions

[jimmiekain]

I have had nothing but WM phones for the past 4 or 5 years so I have become accustomed to a few things. What I really want is the HTC HD2 but I'm not really trying to switch from sprint to t-mobile so I will probably get the htc supersonic when sprint gets it. Problem is, I have never used an android phone so i have a few questions about android...

Is it customizable? No, I dont mean widgets or backgrounds... What I mean is:
Are there custom taskbars?
Custom roms?
Custom dialer skins?
Registry edits?

How is the app selection? That may sound strange coming from a wm user but one of my favorite things about wm is that if i dont wanna pay for an app I can google it or find a torrent for it... Is this possible with android?
If I have an app I really like can I email the install (.cab) file to someone else with an android phone so they can have it too?
When I install an app can I choose storage card or device memory? (If I remove the card will the program uninstall?)
If I do pay for an app will i get it back if I need to swith / upgrade phones?

Does it multitask?
How many apps can I run at once?
is it really easy to switch between running aps like it is on the palm pre or htc phones with the running programs triangle?
Does it need to be reset multiple times during the day?
These are just some of the questions I have about android can someone direct me to a site where I can find out more info?