Yes, you can promote any number of users you like to admin.
If you do, they have all the permissions you have with the exception that you can remove their admin status, but they cannot remove yours. This leaves them a LOT of power within the system to do nasty things if they so chose.
Give out this power very sparingly and only to someone you fully trust.
There is not a lot of granularity for assigning permissions to the CP functions.
What is it you want to do?
