I definitely recommend hiring a contractor. The damage you have looks to be quite a bit, a good contractor will have the tools and know how to repair this.
For help in choosing a contractor and a free e-book go to the website listed in my profile.
The guy wiring the light for free and asking you to tip his helper seems to be reasonable.
If you've hired people to do a specific project I'd say tips are definitely not needed.
Not sure if you've moved ahead with this yet, but if you haven't, I'd get a design/builder. This will be a contractor that does design work too. I believe that will bring everything together for you.