The first, it is more trouble than it is worth. Some programs are sensitive to what username they are installed under, and you'll have to reinstall them. The second, the long shutdown times are controlled by how much data they have to save for the "resume" feature. When you go shutdown, there is a checkbox "reopen windows when you log back in." This will reopen all applications just as they stood when you shut down. Of course the more you have to save, the longer it will take.
Changing your name:
1. Open SETTINGS > SYSTEM > Users and Groups
2. Open the padlock in the lower left corner of the window by entering your admin password
3. Change the name as you want it to appear
4. Close the padlock.
* You'll notice the change immediately if you click your Apple icon and see your "new name" as the last option under "LOG OUT DOE JON"
Shutdown speed issue:
I'm in the same boat you are. I remember a specific "bragging right" that Jobs had when he released Lion was in fact the smaller platform it used, which in turn increased everything else the user did, including start-up and shut down sequences. With time, and unfortunately, a change of management ML did not follow suit of Lion and keep their smaller footprint on the HD.