The horn, itself is good, but no power to same when horn button is pushed.

Need to know if power is thru a fuse  or relay and where it might be located.

Fuse / relay block & position.

If it is the horn buttons on steering wheel... are replacements available?  Through GM or after-markets?

I don't have the owners manual and Haynes give no info.

Any help would be greatly appreciated!  

well here we go. I also have a 90 vette and just last weekend i repaired my horn .the horn consists of two fuses one in the main fuse panel LCD fuse 5AMP and the second fuse is located in the auxiliary fuse block under the passenger dash THEFT FUSE 15AMP.If both the fuses are fine you have to check the relay located under the passenger side dash believe me its there you have to look for it .there will be three relays up there the horn has the orange power wire and the dark green wire that goes to the horn .there is also a red with a white stripe and a black wire.With a piece of wire  and the relay removed cross the orange and the dk green wire if the horn works then with a test light check to see if ther is 12v on the red with white stripe and ground signal on the black only when the horn button is depressed. if no ground signal remove the air bag and check the hrn buttons. good luck