I really miss my MP3 capabilities of my old car so I want to see about getting the single CD/MP3 part and swapping it with the plain old single CD. Mazdaparts has them for 299 but can they be found cheaper?

Are they easy to install?

They don't come with locks or anything do they? My old Cobalt I had to have a dealer do some kind of sync and unlock with the car's computer before I could use it.