Hi there. Few questions, you need both Chrome and Firefox or not? Can you provide a website along with the details of what elements(with the keyword) you want to manipulate, maybe if you can, do a screencast with one or two examples of what you want that extension do be doing? That would be helpful. Or, you can just send that old extension, if you have the source code for it that would be great!
Also, when do you plan to start the project and when is the deadline, if there is one?
Anyway, feel free to hit me up so we can talk more about this, I am very responsive. All the best