Wheel stubs broke off while driving

Drive the old one out and use wheel lug nut backwards with spacers to pull new one in if more than two studs replace wheel bearing.

Which one is it?

Removal
Raise and support vehicle by frame. Remove wheel. Clean and lubricate axle shaft threads, insert punch or screwdriver between caliper and rotor to hold rotor from turning. Remove axle shaft nut. Remove caliper and wire aside. Remove rotor. Disconnect wheel speed sensor. See Fig. 4.
Remove hub retaining bolts and dust shield. Ensure transmission is in Park. Separate hub and bearing from axle shaft using Front Hub Spindle Remover (J-28733).
Installation
Clean mounting face and bore, apply grease to knuckle bore. Ensure transmission is in Neutral. Align hub in knuckle bore, start axle shaft nut and draw hub and bearing onto axle. To complete installation reverse removal procedure. Tighten nuts and bolts to specification. See TORQUE SPECIFICATIONS table.
Fig. 4: Exploded View Of Hub & Bearing Assembly
Courtesy of GENERAL MOTORS CORP.
You can leave nut on end of axle and use a hammer to move axle backwards make sure nut is flush with axle end to not damage threads.

Just becarefull not to break the speed sensor as they are about another $80 of course it may be part of the wheel bearing as well.