I paid a tree service $900 for work. There was a small section that needed to be completed. I paid him in full and he promised to return the next day to finish. 8 weeks later and several phone calls still waiting. I know, should not have paid in full but was trying to help a young person out. I am now at the point of wanting $100 back. I plan on sending a letter next week to him requesting that amount. If I do not hear back from him should I take to small claims and ask for more than $100 + court costs + time for me dealing with this? Not about the money but principle at this point.

... If I do not hear back from him should I take to small claims and ask for more than $100 + court costs + time ...

That's up to you. For $100 it may well be more trouble than it's worth. And keep in mind that you can get a judgment but the hard part may be collecting it.

I doubt if the court is going to add the value of your time to the judgment.

If it was me, I would just chalk it up to experience.