How do I remove & replace a radio/6-cd changer in '04 Outback Limited?

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Have a chance to purchase a used, replacement radio/cd player for our Outback, but unsure how to safely remove hardware around existing radio + the radio/cd-player, & then install the replacement. Appreciate any gudiance, so I can tackle this myself - will cost ~$170 in labor alone @ my service dept, tho they are willing to install a unit I bring to them!