Wahlnutz

I decided to redo my system, I have an after market 4 channel amp running all new speakers but the old system is still there. Of course this caused engine noise ( Yes, i know this is causing it) I never removed the stock amp and its old wiring. I did try once but unpluging the amp made a weird noise. I did redo all the wiring, new speaker wiring and everything. If anyone who could tell me how to remove the amp and old speaker wiring I would be thankful!!