Which MBW? Vintage or modern?
Vintage SD/Subs have the bezel assembly that is like gen; i.e. you have a bezel with insert, a bezel washer, and a retaining ring that seats against the crystal (acrylic). Essentially, you lift the bezel and insert assembly off the case (it snaps onto the retaining ring), lift the washer and then lift the retaining ring from the case. Once the retaining ring is off, the crystal can be pushed out from behind (with the movement removed). Simply snap a new crystal on, and re-seat the retaining ring, the washer and the bezel.
If you have modern, there are some variations in case construction regarding the bezel. Newer models have a bezel assembly like gen; older do not. It would be helpful to know which model MBW you have if it's a modern.