I can see why you're overwhelmed, that's a lot of tasks! I'm fairly experienced with AutoIT and it would take me a while to develop a script that can do all those tasks, specially sometime robust enough to work on many machines. And there may be more suitable tools, such as creating a master image and restoring with Sysprep that might be more applicable.
Start by breaking each task down. Create a test script to tackle only one problem. Don't worry about the user interface, don't worry about the other tasks. Just use hard coded values in the script. When in development I like using "ConsoleWrite" to spit out some debug information while I go. When
When looking at some of these system level changes, see if there's any programmatic API, registry, WMI, commandline tool that can do it. Trying to rely on pure GUI automation (mousemove, click, keystrokes, even controlclick) can be fragile. Your script is doing a lot of admin level stuff so it will need #RequireAdmin at the top.
Admin username / password: Look at Commandline interface via Net: (net User, Net localgroup).
These could be invoked via a Runwait() command. No need to use @COMSPEC because net.exe is separate from the command interpreter cmd.exe.
Password hint may be more difficult
Computer Name: Looks possible via wmic. Looks like you need to know existing name, doable via @ComputerName in AutoIt
Sample wmic code, looking like it's written for batch, is:
wmic computersystem where name="%COMPUTERNAME%"
call rename name="NEW-NAME"
Getting name from excel may be a little more involved, especially if Excel isn't installed on the PC. Look at IniRead, and FileRead/FileREadLine/FileReadToArray for potential options to read from a text file.
To download something via http, check InetGet()
Run programs using "Run" if you'll then need to interact with it, or "RunWait" if you want to wait for execution to finish.
Pinning in Windows 7 at least it's just copying or deleting a shortcut into a certain file. Either per user, or one for global. Check our FileCopy() and FileDelete()
Once you can get the individual features working, then look at starting to assemble them in one script.