I used generator-gulp-angular to generate my project structure. I chose regular javascript at the time. Now I want to use typescript. How easy will this be, or do I need to re-generate the project structure?
You can regenerate the project in the same folder and Yeoman will prompt you on file conflict (so you'll see what is changing and you'll be ready to fix these conflicts). Then, just make changes to the new code so it match your app if you diverted from the original app code.