I need to know where to find and how to replace and or repair horn for 1999 C-5 corvette.

you can seach on www.
i think you will be seeing it

When you remove the cardboard like black splash panel on the rt front passenger side you will see the horns. Bolted on with a single bracket.
Had one of mine short out. Replaced it with a junk yard special not a $60 or $70 dealer part. Two different notes HI and LO. Get the right ones. Similar new horns at Advance and AutoZone.