I think it depends on the material. I've tried to have a pair stretched out in the toe, and they're made of a very thick leather. The cobbler tried twice, and I can just barely notice a difference, but not much. I'm sure that if the material were softer and thinner, that it would have been more successful. Anyway, it did seem that they were able to target a specific spot, if that is more your meaning. Definitely take them in and give it a shot!
Yes, I've done this to a couple of pair of boots over the years with varying success. It's definitely worth a shot as I've never had shoes ruined by this process. It does depend on the leather and also on the skill of the technician, so take them to a reputable store Karen!