Here's a good post about horns: http://www.brickboard.com/RWD/index.htm?id=745258

With regard to your brakelight, try taking the brake light sockets out of both the left and right sides and switching them. If the problem follows the socket, you know you have a bad socket. Although the sockets seem simple enough, and sometimes you can fix them by sanding the contacts and bending the metal a little, there are times when they go bad without any visual reason why. Just replace it with one from FCP, the junkyard, or the dealer.

If you swap the sockets and the problem remains on the right side, you've got a wiring issue that once again you just need to chase down with a tester. Usually it's on the PC board inside the light housing, or the connection going to it.

By the way, with a 240 you always need to change bulbs in pairs. If you changed the right side brake light bulb make sure you change the left side also. If you only change a bulb on one side and not the other, the bulb failure indicator light will stay on, because it senses a difference in resistance between the old and the new bulb. It will sometimes even catch the difference between two different manufacturers. Always change in pairs with new bulbs of the same brand.