Huh, you don't need scripts to make a skill shop, It's just a choice, tied to condition branches/variables.you need a script to do that - there are two or three skill shop scripts (or common event shop script, which do the same if you have the common event learn a skill) available on the master script list.
If you're new to RPG-Makers, follow the link in my signature to find the master script list (and a lot more tips and tutorials)