A broken stem can damage more than the stem
If part of the stem remains in the movement or the setting mechanism was damaged when it broke, the repair can extend beyond fitting a replacement.
Screw-down crowns also depend on the case tube
On divers and sport models, worn crown or tube threads can affect sealing and usability. Water resistance should be tested after relevant case work rather than assumed.
What the crown does helps narrow the problem
Tell us whether the crown pulls out normally, whether the watch winds, whether time/date can be set and whether the failure happened suddenly.
Original versus compatible parts
Part choice depends on the model, availability, customer goals and whether originality matters.