Post some pictures if you can. How many studs are broken? Are they broken off flush, above or below the surface of the knuckle? Are the ones that are broken screwed into blind or through holes?
The knuckle is critical, I wouldn't want to damage it in any way that would weaken it. If you are willing to give it a whirl yourself there are a bunch of different methods. The other option is that you pull the drivers side down until you have a bare knuckle and take it to a machine shop.
Rule #1... Never ever break off a hardned extractor or drill bit while trying to extract a broken bolt-screw-stud. If you do break off a hardned tool you are pretty much doomed, as it will have to be removed with carbide tooling or a plunge EDM machine (tap disintegrator)
As long as you don't violate rule #1 you can do it.
Clean up the part.
If it is broken off above the surface find a larger nut to slip over it. Weld the living daylights out of the nut, then quench with penetrant and or water depending on how comfortable you are with fire. Attempt to unscrew...
If it is broken off at or below the surface drench it with penetrant. You may be able to unscrew it with a punch and hammer if you can dimple it near the edge then strike the punch at an angle attempting to turn the broken part counterclockwise.
If the punch does not work it is time to get out the drill...
Personally I like to drill two or three small holes right at the edge of the root of the thread on the broken bolt-screw-stud. Always use a center punch to accurately lay out the holes. After the small holes are drilled I center punch the center of the bolt-screw-stud and drill a hole large enough to reach the small holes I drilled around the perimeter. Usually the remnants can be extracted in one piece with an extractor, or use a pin punch and break up the remaining bolt-screw-stud into 2 or three pieces (depending on how many holes you drilled around the perimeter). Hopefully that leaves you with a threaded hole in serviceable shape.
If that does not work and you have to drill out the entire mess...
Do not try to re-tap it. Buy a Helicoil kit, yes they are expensive, but it will give you a threaded hole stronger than it was originally.