Changing owner globally

[Stephen Jonke]

I know this is possible, but I don't know how to format the command and 
want to make sure I have it right. My sisters Mac running 10.3.4 was 
originally set up with a particular use (her Ex) as the admin and so 
lots of files are owned by his username. I want to remove his account 
and change all files on the system owned by him to be owned by her. 
What is the find (or other) command I should use to do this in one fell 
swoop? I presume I should first change ownership and then delete the 
account (what happens if you delete the account of a user that has 
ownership of files that remain on the system?)

Steve