Here are some quick answers, if you need clarification someone else can do it, haven't got the time atm
1: If you are after a glass effect where you can see the desktop then its impossible. Messenger does not support it. Otherwise just replace the 20061 image.
2: Moving the infomation bar causes bugs, but you can remove it by wrapping a blank element around it and setting its layoutpos to none.
3: 920 Style
4: See #1
5: Look in the definition file of that window, its pretty obvious which one you have to get rid of. (windowicon element)
6: Just move the elements around or edit the layoutpos value
7: Wouldn't attempt to try this unless you know how layouts work properly, it can cause a lot of problems. If you are a new skinner I wouldn't try it just yet. Explaining this would take time that I don't have atm
just know that moving elements around drastically will most likely cause issues.
8: see #7
9: No image file, its code controlled. If you look for the word "caret" in definitions you will find it. I wouldn't remove it since its a UI convention which shows that something will dropdown when the user clicks it, but you know whatever.....
10: Yeah no way, that's not how it works. Some borders are code controlled while others are merged with images. The ones that are merged with images you have to edit manually (and even still you won't get what you want). The code controlled ones there is no chance you can get the effect you are after.