I found this series of videos from Sailrite to be very informative. Sailors by nature tend to be very resourceful with doing their own repairs, and this series certainly supports that.
I’ve done a few spot repairs on my own sails (e.g. replacing telltales, small patches). After watching these, I am willing to try some larger ones if needed.
There are 13 total videos in this series.
Enjoy!
Massabesic Swim Club 