I haven't done it myself, but if you dig a bit in StackOverflow for examples of how folk have overridden default styles for the controls you should find a couple examples.
re: gradle issues
I'm not sure how you're running things on your side, but the workflow for me is:
1) Fork module
2) Import forked module into my project in the Trigger Toolkit
3) Hit update inspector for iOS & Android
4) Open module in Android Studio
5) Develop as per usual inside Android Studio
6) When it's time to do a release, either select "updateModule" within Android Studio or drop to the command line and:
Drop me a ping on email@example.com if you're still not having any luck with getting gradle running.