The one time I tried to remove the entire pedal assembly I found that a huge wire bundle was woven through the bracket so the assembly couldn't be removed without cutting the bundle. Instead, what I did was simply remove the automatic brake pedal pivot bolt, then the pedal, and then slipped the manual brake pedal into place. It won't stay there by itself because the brake pivot bolt is shared with the clutch pivot bolt on the manual assembly, so next, I unbolted the clutch pedal and bracket from the manual pedal assembly and bolted it onto the side of the automatic pedal bracket while still in the car. You'll need to use the long pivot bolt from the manual pedal assembly since the one you'll remove from the automatic pedal will be too short.
Here are a few pics of what I mean. The orange bracket in these photos is the clutch pedal bracket that simply bolts onto the side of the brake pedal bracket.
