BeeUtifulDisaster002

I have a 2001 Tahoe, and 2 days ago we hooked up a Dual double din CD player. The previous owner had a system w/ amp hooked up, but the amp is no longer there, the factory stereo (Delco brand) was in it. They had cut the factory wire harness, & it was taped back. We had trouble at first with the stereo, first it was getting no power, then it was no sound. Somehow, while trying to find out why it had no sound, (which we now are pretty sure is bc of the factory amp) the dash gauges, front & rear wipers, and AC/heater & defrost quit working.
I've hooked up stereos before & have never had this kind of trouble.
We checked all the fuses in both fuse panels, under dash & the hood & switched different ones out & changed a couple, but it didn't fix anything.
Also, as far as the factory amp not letting sound through the speakers, is there a fuse or a certain wire that we need to check? Or just bypass the amp (how to bypass the amp is about the only search results I've found} Thanks