The answer to both questions is yes.

By default, individual cells are set to "Locked", but this only comes
into force when the worksheet is actually protected. So, you need to
unlock the cells that you want to allow users to change, and to do this
you need to highlight them, then go to Format | Cells | Protection
(tab) and unclick Locked. Then you need to select Tools | Protection |
Protect Sheet and you have the option of password-protection (you will
have to enter it twice, but choose something memorable).

If users try to edit a locked cell they will be told that they can't,
but they will be able to edit an unlocked cell. They can't change
formats or column widths, and will not be able to change the name of
the sheet.

Hope this helps.

Pete