I just bought another max and it has an oldschool built in car phone with a handsfree thing wired in, theres a mic by the driver's side windshield pillar, can i wire my phone into this system? any advice? experience?

 

No you can't. The old phone systems are analog, and the new digital phones will not interface with it. All cell phone kits are phone specific except those cheapo strap on units. It will even cost more to have an analog phone activated because the service takes more power to use.