Noobie intro and 2 questions

[Merlinspop]

Greetings, all. New '07 Nautical Blue Sedan owner here. Live in Charles Town, WV and commute deep into Fairfax County every day. Got tired of feeding my Dodge p/up wads of money every other day.

Anyway, on to my two initial questions:

1) So far, everything about the Yaris has lived up to or exceeded my expectations, except that I hate the horn. It's not very loud, and the tone just doesn't project as well. What I'd like to do is swap the OEM horn out with something with more 'beef' like the hone on my Honda Goldwing. I've searched, but haven't found any details on how to easily get in there and whether there are any electrical issues to be aware of. Any advice is appreciated.

2) I have a gps/xm/mp3 that I'm using. I'd like to keep the 12v accessory plug free for other things and reduce wire clutter by hardwiring it in. Any help or direction in this is also great.

I did search both of these topics and came up empty.

Thanks,

B