Ok, this is the closest site of the OEM footwell LEDs for the Versa. I can't find any sites that have a cheaper price
http://www.nissanonlineparts.c....aspx
Definitely change out the factory horn for an aftermarket one, it's an easy mod and worth it IMO. You can go to checker/schucks/kragen auto parts for it.
The interior lights like the dome and map lights go to V LEDs and you can find them for the versa. I can give you the part number for them. The part number is DE3175 and they take less than 10 minutes to change out.
http://www.v-leds.com/
Other than that, if you have any questions, give me a hola.