De Installing Amp Which Wire to take out?

Ok i gotta return my amp back to my friend. Do i leave the + wire from battery connected and only remove the - from battery to chasis? ANd then go ahead and disconnect power and ground and rcas from amp in the trunk? Because im going to just be swapping amps. Is this the way to do it or do i have to remove both - battery to chasis and power wire from positive to amp from the battery aswell thanks.

if you remove the fuse from under the hood so the power wire isnt hot you should be ok and then you wont have to disconnect the ground cable from the chas.