Hi, and welcome to the forum.
The answer really depends on the extent of the damage. If it's completely worn and requires full replacement then you would do best to remove all the spars, remove the fabric that's already there and use that to create a template for a replacement. Sewing these heavy materials can be done on a home sewing machine but it isn't easy.
If the spine has punched a hole through the nose in a single spot, then you could do at least a temporary repair with a fat end-cap on the end of the spine (it might have one, but that might have got punched through and lost or split,) and a rectangle of dacron folded over and slipped inside the nose webbing at the tip of the spine. I've run a couple of old kites like this for years with no problems.