Before you do anything, look at the breech face. If it has a threaded plug where the pins come out the front, as in the BT-99, then you have the old model Citori. Parts are not widely available. It takes a special tool and an impact driver to remove the plug, if it will come out at all. :^(
If your gun does not have two or three holes around each firing pin, you have the newer model and the above post applies. :^)
I also suggest new mainsprings and top lever spring.