Does a 2006 Toyota Corolla use a horn relay I want to replace the horn and dont know if there is already a relay in use?

Yes. I have a '98 Corolla which has a horn relay. Look under the hood on the driver's side. You will find a weatherproof fuse box over the left front fender. Fuse no. 10 is for the horn. To the rear of the fuse box, you'll find another weatherproof box which contains the relays--all clearly labeled, including one for the horn. The horn relay in my car is a Toyota 90084-98031 TN156700-1070 12 volt, made in Tennessee by Denso. Most horn relays pass 30 amps, so I'm safe in assuming mine will pass at least 10, which should handle any horn which fits in the car. The stock horn may be OK for quiet neighborhoods, but it's useless for keeping an 18 wheeler from merging into you on noisy freeway. I'm installing a switch under the dash which will allow me to select which horn I want--one position for a stock, polite "beep", and the other for an obnoxious, twin-Trumpet, 135 db "B W A A A A P ! " when I need to scare the $#!t out of some moron. Whichever horn I have selected will be controlled by the stock horn button.