[Unity Pro] How do you open and modify AssetBundles?

So I finally redeemed my free trial for Unity Pro and I want to open and modify an existing AssetBundle. I have no idea how to do this and have not found any useful information in the Learn area, but that might just be because I can’t script for [insert swear here].

I have not used AssetBundles a lot, but as far as I know you cannot modify AssetBundles. To modify it you basically have to create a new one and include the modified content. The reason for this is that AssetBundles are often meant to be downloaded and used by the EndUser, if it was modifiable/readable the EndUser could open the AssetBundle outside of the game and have access to all the source content and files.