Firstly, congratulations all the book sprinters. You did well. I'll be having a good read of it this weekend.
Before I delve into some code I'd like to give you my motivation for doing what I'm about to describe.
I need image uploading, ease of use and consistency. I also don't want to bother with maintaining 2 versions of fckeditor. I knew it shouldn't be too hard to get it working across to 2 systems and to be honest it wasn't. It took a little more to find out what the Image assist module needed though.
A nice feature of fckeditor is that we get a nice button in the editor toolbar instead of the link below the textarea as it would normally be. To get fckeditor and image assist working in drupal together you will need to copy img_assist_fckeditor.js from fckeditor module folder into img_assist folder. If you get a white empty popup screen then you have missed this step out.
On to some actual coding. Please make sure your drupal modules are all working before trying this for your own sanity's sake.