New user purchasing an X5 needs help and recommendations

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Hi. I am new to the board and wanted everyone's well informed advice on a few things. I am looking to buy an 02 or 03 4.4 X5. Navigation,Sirius,and the ability to use an iPod are a must for me. I realize that those years don't have a Sirius option built in but can I somehow retrofit a new X5 stereo into 02 or 03? If the vehicle doesn't come with navigation can I add an OEM unit to it? With the iPod is there anyway I can use it and have full function even with the navigation? I realize these questions have probably been asked and answered a hundred times but I couldn't find the specific answers while searching. Also if you guys know of anyone selling a vehicle that fits this criteria please let me know. I just sold my car and need something in the next few weeks. Thanks so much.