the dealer wants $275.00 plus tax instead of tightening it from the inside

 

If it is just loose, you may be able to repair this yourself.

When I bought my 06, the passenger side door handle was completely shot. I was able to take the door apart and tighten up the guide rail and it is like new now.

 

Found the thread I used to fix mine:

https://mustangforums.com/forum/2005...sit-flush.html

 

Seems I saw a vid on youtube that shows you how to fix this also.