Replacing plastic top on 5 Series Touring

This morning I had a garage roller door come down on me (it was up when I started going through, I stopped in the wrong place when I saw it coming down, it ignored the 'go back up you f**ker' remote button.. and it didn't have a sensor!)

It's damaged the plastic top of the boot on one side, breaking the fittings underneath

Has anyone replaced one of these before and if so, how involved is it?

Thanks

(I am in Japan)