It is quite common for young people to have doubts about their abilities to do the variety of jobs required on a missions project. Most have never mixed concrete, laid bricks or blocks, hung drywall, installed lighting fixtures, taught school, led Vacation Bible School, etc. However, they all want to do their best. And when the trip is over, they want to leave knowing that the job was done to the best of their abilities and that it was done right.
Ask God to help you trust Him in using your abilities for Him.