Uploading hundreds of files or changing thousands of pages can be tedious. Limited automation is allowed on Wikipedia as long as it follows certain policies. The easiest way is to use AutoWikiBrowser.

Or, you always can grab your favorite scripting language and write a bot, but there is no need to reinvent the wheel: most modern programming languages have a MediaWiki library already written, there is a full list or programming languages and libraries here. Once you have written the code, you can request approval to trial run your bot. Once approved, your bot will be flagged, so it can be hidden from the list of recent changes. Alternatively you can request someone else take care of the whole matter for you.