Audio-cassette player with nav system on 2003 CLK320

Hi,

I just got a new CLK320 coupe with a 6-disc CD changer and a navigation system integrated. Although I like the ride and everything else, I am sorely missing an audio-tape unit. I am one of those, who has a huge collection of audio-tapes, which I would like to use, and do not think it's practically possible to convert them to CD's.

Installing the navigation system has deleted the audio-tape player.
Before the sale, the dealer mentioned that I could connect an audio-tape unit to the glove-box, like the glove-box CD changer, omitting the fact that I could not use the in-dash controls to play/stop the audio-cassette unit.
The only solution the dealer has is for me to insert a walkman into the glove-box and push the play/stop buttons on the walkman while driving, stretching across the passenger-seat to reach the glove-box!

Has anyone added an audio-tape player to their car?
If so, can you please give me some more details?
I would really appreciate it.