What bothers me ... is this is why we go to sign school to learn... excuse the rant
I know this is a forum and we are here to learn, teach, share etc. and I'm glad to.
But did put a ladder up there and touch the surface plus measure. ?
Is it flex face or plastic of some type. ?
Did you see how it might come out screws or rivets on frame ends or top. ?
Do you know about how long that sign has been up there. ?
Do you have or able to get equipment to safely to finish job. ?
Your in a big city what about sign permits. ?
Common sense questions
Doing this type of job is not hard, but these questions need to be answered to deal with this.