I think that and the Marque is going to be my biggest expense. Woudl it be easier to refurbish the marque or start from scratch.
Probably depends on what you have to work with now.
Some of those old marquees were made with a lot of sheet metal and angle iron. Others were made of wood.
You could have a rust problem, and a lot of metal to fabricate... or a rot problem, and a bunch of carpentry to deal with.
If it's backlit plastic, you probably need a sign company to take a look at it. For that matter, having a pro look any design over would give you some idea what you're dealing with, whether you decide to fix it yourself or not.