Replacing my bottom bracket. I need help IDing a replacement
You have done your homework correctly. You need a square drive bottom bracket with a shaft length as close to 125mm as you can get to fit a 68mm frame. I have taken out quite a few of the plastic cup units with no issues, but I prefer the metal one. But that is just personal choice. Take a look at the area of the chain stay (the tube from the rear axle to the bottom bracket) for crank clearance. Some frames run the big ring very close and bringing the crank closer may cause an issue. You can use a shim behind the crank- side cup to move it out to the same location as original. It is doubtful you will notice the difference if the nondrive side is a mm closer to the centerline. you will likely have to fine adjust the front derailleur when your done.