Any suggestions to replace the old stereo with CD? I'd love to have something not too expensive that would play MP3 and links to the iPhone.

Try the search facility as there is plenty of threads to give you an idea. Once you've done that it will depend on the system originally fitted to your model what is possible. There's also plenty of info regarding sat Nav screen, cubby hole if you don't have a screen fitted from factory. After you've immersed yourself in all the options then you'll have a better idea what's possible and someone will point you in the right direction with what you've chosen.  MY15
Tyre Pressure Monitoring System (TPMS)
Surround Camera System
InControl Apps soon to be replaced with CarPlay (WIP)
Meridian Premium Surround Sound
Digital Audio Broadcast
Timed Climate
Cruise ECO Data
Follow Me Home Reverse
Extra Features Menu
Picture In Motion
4x4i screen (WIP)
Digital Broadcast TV
Meridian Rear Media with WIFI
Factory Powered Tailgate
Blind Spot Monitoring (BSM)
Reverse Cross Traffic Alert (RCTA)
Electrochromatic Wing Mirrors (WIP)