Newbie creating a large-scale, multi-language software training

In a nutshell - My team is going to have to create a software training "guide/site" for a tool, in multiple languages, and multiple parts.  I have not done any "eLearning" courses before, so I am overwhelmed at the magnitude of this, reading everything I can to try and understand the challenge we are undertaking.

Specifics - This software tool is very robust with lots of highly detailed steps.  Our audience will be mainly researchers looking at data.  However, some won't be that interested in the highly detailed steps and just want a quick overview.  Mgmt has stated they want step-by-step instructions (assumption, viewer watches a video), and then allow for a try-it simulation of the same content.  And respondents need to be able to skip around to find the answer to the question they have, but each module also needs to be linear from a task-based perspective. This software tool is customized specifically to every client, so we'll have to redo each screenshot/screencast for that client specifically.  And if all that wasn't enough work, we will also have to publish in various languages.

Specific questions - I might be wrong, but I think it would be better to have separate specific modules, with a link to a main menu so respondents can choose the module they want to watch/try.  I'm assuming that would mean each module would be a standalone storyline project, published to the web, and the main menu would be a separate storyline project as well, but with links to the other module URL's.  Mgmt didn't like the look of the built-in Storyline player, but I don't think I can customizing the player (like I've seen on lots of way-cool examples) because my screencasts will cover the background? Is that correct?

All in all, I welcome any suggestions!  I've been reading all I can up to this point, but since we just bought this program, and it's not like I have any experience with creating anything else like this, I currently feel very out of my element - not only do I feel like a complete newbie, but a complete newbie who is responsible to produce quality work very very quickly.  Yikes. 

Any help / point-in-the-right-direction / heck, words of encouragement would be greatly appreciated! 

ps - I'm also the liason between the researchers who will be creating the scripts, and the graphic artists who will be creating the content; yet another challenge to overcome.