The most important advice I can give you is to trust God and depend on Him for wisdom as you make decisions. Don't depend only on your own wisdom or experience; look instead to God.
And you can trust Him to help you, because if He gave this responsibility to you, He'll also give you the wisdom to carry it out (if you seek it). Remember: You are not alone. God is more concerned about the welfare of your church than you are, and He knows what is best in every decision you'll face. The Bible says, "If any of you lacks wisdom, he should ask God, who gives generously to all without finding fault, and it will be given to him" (James 1:5).
Let me make two other suggestions that might help you. First, be a good listener. What concerns do the members of your church have that the board should be addressing? And what can you learn from those who have been leaders in your church longer than you have? The Bible says, "A wise man listens to advice" (Proverbs 12:15).
In addition, seek God's will for your church and its ministry -- and ask Him to help you and the board put it into action. Don't be satisfied just to keep the buildings in good shape. Ask God what He wants to do in the lives of your members (including your youth), and also in the lives of those around you who don't know Christ.