rename a computer

Yes, you can call an iMac whatever you want.

1. Open System Preferences.
2. Click on Sharing.
3. Click on the field Computer Name: at the top.
4. Highlight the current name and enter a new one.
5. Press enter or click anywhere in the window outside of the text field to set the new name.

No not at all. When you do the migration, simply connect the old Mac's Time Machine External Hard Disk using a USB cable to the new computer. Do this before the new computer is turned on for the first time. When you turn on the new computer it will startup Setup Assistant. SA will get to a point where it asked if you are migrating from another Mac, simply type YES and follow the on-screen prompts. This is the fastest, most reliable and easiest method!!! After the migration is done and you have the computer setup, then you can rename it if you want to.