Thanks for all the responses so far.
edrach: I know that aux CD player mounts below the stock tape/radio (I've seen it on other vehicles). What would be on my mom's legacy now in the space where the CD would go? Is there just a flat panel there? I'm trying to remember but can't... And yes, I'll be sure to check interchangability before buying anything online...
cookie: I don't believe it's a clarion, but I may still want to take you up on your offer and buy a harness to hook it up - let me get back to you...
roda2003: that's exactly the type of thing I'd do on my own vehicle, thanks for the idea. But for my mom, it would make her nervous, having so many presets That's one reason I'd like the stock CD player that came with those legacies - she'll feel like it's still her car, and that I haven't "changed" it.
Again, thanks.