Ford Repair: Fuse Diagram, fuse tester, haynes manuel

Question
I'm trying to search the web for a diagram for the fuses for a 1986 Olds Calais.  Can you help?  My son is the owner of this car and recently got a "fix it" ticket because the the tail lights were out when the headlights were on.  They had worked previously but had quit all of a sudden.  I did get a fuse tester and checked all of the exsisting fuses and changed 2.  Don't know what I changed, but I knew they were out.  The lights worked for a while and then went out again.  Help!  I'm a female with very little car knowledge and very few funds.  Any suggestion would be welcomed.  Thank you.  

Answer
LISA

you can get the diagram from a haynes manuel. you can get it from autozone or other auto store for less thsn 20 bucks. i dont know of any web site where you can get the diagram you need. if you replaced the fuse and it blew again, you have a short. hope this helps.

ken