Just a heads up before you get it done.. Do a search for "Tint Scratch".
I found out the hard way (although got it replaced free of charge) and scratched the tint on each door.
The E90's (and assuming 92's etc) have a hard plastic gutter (for water??) just below the felt on the inside of the door skin. The smallest piece of dirt will leave you with scratches everywhere.
You'll find in your searching "Moleskins" which are stick-on felt pieces to suit (or make your own). They seem to do the trick.
I went 35% (darkest legal in ACT), although wish I went darker..