My guess is that you can bring it to the LBS and get exactly what you want if you bring enough money. Modifying a triangle from my Project Management training, you have a choice.

At a good shop, you can get it done Quickly, Right or Cheap... Pick any two.

Offer them enough money (to get put ahead in the line) and you can probably get it done quickly.

Since cost is likely to be an issue, and we all want things done right, then you probably have to wait your turn.

Others have suggested it, and you have shown no sign of going there to look, so I'll try it again. You should really try to go back to the shop before you destroy your shifter, and YOUR Tiagra shifter really does turn into garbage... or go search the guidelines at some of the sites suggested above like http://www.parktool.com