By shifter interlock, do you mean the piece that is activated by the key - mechanical connection to the switch? Or the piece that is activated by the Brake (solenoid) to prevent moving to gear without brake engagement....
The mechanical interlock is somewhat easy to adjust.
The flickering gear incator is very likely due to dirty (or burned) contacts on the white major switch assembly in your photo. (Search forum, there are ways to clean it). It is a bit of a pain with the 95 interlock but can be done.
Scott
1995 BMW 525i w/139K miles, EAT Chip - (Gone)
07 525i 22K, 07 328xi (41K)
1982 Mazda RX-7 w/147K miles (Back again!)