Lights

Hey, im having problems with my dash and taillights. I had just installed an after market stereo and got the right wires via trial and error but now my dash and taillights are blowing the fuse when i turn on the headlights; not to mention my command start is doing the same when i try to use it. i checked the taillights for corrosion and all that simple stuff but i think it has to do with the bnackwards wiring in these cars. can anyone help me?