My OEM CD player in my car crapped out, and I set about to research how I might replace it and add the capability of playing cassettes, since the local library has literally thousands of books on tape for free.
I went to all the local car audio places and, naturally, I was treated to a parade of morons and opinionated know-nothings who predictably told me that 'They don't make that anymore..' , which means 'We don't have it in stock.'
I got on the web and looked at Crutchfield.com. They list all the possibilities that will fit your particular car. In the case of my Mazda, the CD-Cassette combo wouldn't fit, but they had a note to call their toll free number and discuss it with them, because there could be more than one way to skin a cat. Called the guy, he made a recommendation. I ordered the Kenwood components Friday, and they were delivered Monday with specific instructions for my car, custom harness adapters, tools to get the old box out, and I was done with the installation within 2 hours.
Works great, sounds good, looks good.
Sorry to go on, but competence is remarkable these days.
They gave me a bunch of '$20 off on a $200 sale' certificates to give to my friends, which would get me additional discounts if I wanted to buy anything else, which I don't. Email me if you want one.