find and replace, ad infinitum

Dear DevShed,

I am interested in a shell script to use in the darwin UNIX implementation on my MAC (running OS X 10.2.8) that will perform multiple [possibly hundreds of] find and replace functions within a document.

As an example, if I had document that contained, among other thing, the names of teams in the Nat'l Football League, and I wanted to replace these with all of the corresponding team names from Major League Baseball (e.g. NY Giants -> NY Yankees, New England Patriots -> Boston Red Sox, Philadelphia Eagles -> Philadelphia Phillies and so forth), is there a script that could make all of these changes at once? (Or maybe a variation on/modification to sed?)

The script I envision would include the names of all of the find(football) and replace (baseball) pairs. I would be using it over and over on many documents with similar content.

Thanks,

ml5003