Noesis

Very easy, electrically, they include everything you need. Mounting wise it depends on the car or truck. On a Cayenne I'd mount them right up front. They include mounting hardware, but it still might take a trip to the hardware store/your garage to find hardware that works for how you specifically want it mounted.

A few examples, you can see the hellas behind the grill, it actually looks cool imo:
http://www.youtube.com/watch?v=-vZg_cdITwg
http://www.youtube.com/watch?v=j7VH-6158RI

Comparison of a stock horn versus the hella:
http://www.youtube.com/watch?v=wFe9njz5NeY

After you do one, you'll probably order them for all your and your family's cars. They are a good balance of spl and practicality. With car stereos now days, people on cell phones and whatever else, there are a lot of people doing everything BUT driving, while they are on the road.

rome

Even thugh your original bumper to bumper warranty has expired, the repair work previously done to the horn may still be under (a repair work) warranty. Because the horn is a safety issue, I think if you push the dealer hard enough and focus on safety and the prior repair work not holding up they willprobably fix it for you.

I'd think the last thing they'd want is a lawsuit because of an improperly (twice) repaired horn.