'91 300SE with MB sound system

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I am thinking of installing a new XM capable satellite radio in my 300se. I have the original Becker with MB sound system that works fine. Has anybody installed a different radio and if so:

1. Do I keep the existing amps in trunk or are they bypassed ?
2. Does the tuner in the passenger side footwell come out also ?

I have the wiring diagrams but am not sure at what point to install the new radio.

Thanks for any advice.