I'm pretty sure I know the answer to this, but any idea how difficult it would be to make it work, or if it's even possible?

Most importantly, I want to replace the rear fender on my '07 883L. I found a guy who's selling his 2000 fender.

 

It would be more difficult than finding somebody selling their 2004-2013 fender...

 

Yes it is possible and not that difficult as I just did it to my 07 custom. I didn't like the fat fender look on a sporty. I did have to us spacers between the fender and the frame rails and that leaves what to do with the ECM. Since I also went with an early sportster buddy seat all my electronics fit nicely under the seat.