i know by now everyone doesn't want to hear about people's stereo issues, but i just need to know like two things that aren't really clear in reading the numerous old postings on this forum.

so i am going BACK to my old stock stereo, because i'm too broke and lazy to buy a new one after the old one was expropriated against my wishes. the DIN plug still is connected to my amp, but the many-wired harness was unplugged from the amp (because i had an after-market radio in there once). so i plugged it in. that didn't change anything -- my old volvo cassette player still don't even turn on when i've plugged in the DIN, harness and power. so i need to know: is that harness and DIN and (maybe even) power all somehow bypassing my amp, even though a very similar looking DIN plug and harness are connected to my amp? was much wire-cutting and reconnecting needed during the installation of my old aftermarket radio -- and do I have to re-do that in order to get my even older VOLVO radio back in there?

i REALLY appreciate any help anyone can give. THANK YOU!