I have a 2000 jeep grand cherokee laredo and here is my snafu:

I failed inspection and was told I needed an upstream and downstream sensor. I bought them and while looking at youtube and diy sites I came across a note that said " its rare to have both go out at same time so first check your fuses. So I opened fusebox and found the receptacle marked for 02 sensor. There was no fuse in that slot. Went to parts house and bought fuse. When I inserted fuse it was loose. Pulled out and noticed there were no visible clips in receptacle to grab fuse. Parts guy said I need whole new box. I then preceded to pull all fuses out of that section of box so I could get a better visual on the part I was looking at. Called dealership and they advised that the fuse I was focusing on was unrelated to my emissions. So I inserted all fuses back in. Now car won't start. It turns over but the antitheft key comes up flashes once then stays lit. Dealership advised that I would have to reprogram key as the car has lost signal with computer. So I called auto locksmith out. He supposedly tried reprogramming key but did not work. Any tips, tricks, advice, knowledge or sledgehammers greatly appreciated! Thanks