Maybe you shoud do loops near your area if you are afraid of technicals.
This year I had to prepare for a very long mnt bike marathon and since there were rarely people who were eager to ride 8 or 9 hours per day, I rode alone most of the time. I wanted to do the marathon more than I hated to ride alone. So, I took trails that are near my home and did loops so in case of a technical or some accident, I was able to go home quickly.
Changing a flat tire is easy so you can learn how to do it.
I also think you'll be able to do the century but it's always better to be self confident and prepared.
Good luck!