1998 expedition amp n sub

We recently purchased a 1998 for expedition, and we are lookin into putting in my 15" sub, and my amp. Well when opened back side door panel, found a 8" sub w amp. Well sub was blown so we just disconnected it, well he went to cut wires, and now the stereo will only play thru headphones from the middle seats. He says he hooked all wires back up like they were, checked the fuses, but still wont work. Are we missing where there is a fuse box that maybe he needs to check out? What is causing only the headphones to work? We have no sound period thru speakers.. We do not have a manual for it, there for some reason was not one with the vehicle when we got it.. Where else in the vehicle woudl there be a fuse box to check? Does anyone have any idea as to what he might need to do???????????? Thanks

There is a fuse for that amp, it is in the fuse box under the hood.