Its nearly impossible to do, especially on an old hinge.... well impossible w/o breakin the hinge or scrapping some paint....
When mine broke, by mistake I put the hinge in w/o attaching the flap, though I could do that after the fact, and spent at least 90 mins trying to get the brand new hinge out w/o breaking it.
I think I used a total of 2 micro screwdrivers and a normal one in the process to get it off.
Current
2008 M5 6 Spd
2000 Z3 2.8 5 Spd MSport
2012 X5 35d Sport
1995 540i 6 Spd
1992 535i 5 Spd
Former
1995 530iA
1986 635CSI 5 Spd
2011 X3 2.8 MSport