Tail lights and gauge lights aren't working..

Hey guys, and gals! I have a 1989 chevy k1500.
I have a bit of a story on this one so bear with me
here. I bought this truck for 200 bucks from a friend
and everything was working. I wanted to put in a
new radio and so I started fidgeting with wires. I got
everything put together and that night the gauge
lights didn't work, then I found out about the tailight
a by getting a 106 dollar ticket that same night. I
thought maybe it was a fuse so I replaced every
fuse....  I followed the wires from the tail lights to
inside the truck and everything looked immaculate
besides from the out side of the wires having a bit
of mud on them. I looked at the connectors and still
looked totally fine. then I changed out all of my
bulbs that didn't work so then I moved onto
replacing switches. I need help please!!! This is
confusing the heck out of me and it's driving me
insane! The reason I mentioned the radio is maybe
it has something to do with that??? its been almost
3 weeks