My 88 park avenue need help asap

Hey I have a 1988 Buick park avenue. I was having problems with my tail lights and running lights not working and I checked every wire and every bult and couldn't find a problem. My dad who has been a mechanic for over 20 years said it was probably the switch so I installed a new one. And now the fuse for the tail lights blows as soon as I turn them on. I have checked everything I could possibly think of and was wondering if anyone had any ideas for me to try

Sorry guys forgot to tell y'all its got the 3.8L v6 engine in it

No quick answer here, get a wiring diagram and trace the harnesses to check for a pinched wire, disconnect one side at a time to help pinpoint the source.

Max, did you notice the date?