Noob here! With lotsa questions

Hi i just bought my first Ford. its a 2005 Crown Vic p71 ive always wanted one finally got one, its got 133,000 miles. the driver side headlight doesn\\'t work i did some research and found out they have bad LCM but you can fix it for a dime. I did the external relay soldered a new one in and the driver side head light still doesn\\'t work on low beam ONLY it works with high beams. the bulb is brand new. is it a wiring issue? I work at a GM dealership and was told that it has something to do with the Hi/Lo beam lever or the head light sector switch. I would like to find out how to fix that, in the mean time ill drive around with my brights on all the time. The car still has all the VHF ants on the roof it has 5 i wanna hook those up to a VHF scanner. it also has two working spot lights. I just put a JVC head unit in the dash. but the door speakers dont work. I wanted to run a CB radio and Ham radio setup. I just replaced the stock mufflers with flowmaster super 44s (2.25) with stock pipe. it sounds stock it didn\\'t make a bit of deference except when you get on the throttle it roars a little bit. whats the best exhaust setup to run on this car? this winter i wanted to do a full exhaust with headers. what would be the best setup?! Can anyone tell me some basic facts about the car the common problems with them and some mods? Some engine mods some specs about my car? i think it has 3.27 open diff when i do a burn out it burns the right side only so im guessing its an open diff. i wanted to trade the 3.27 for 3.73 gears where do i get the diff gears from? what are some mods you can do to this car? sorry for all the questions but when i get a car i want to know everything about the car how it work all the problems and what mods can be done. i came from driving northstar Cadillacs so this is quite an upgrade ;) first Ford owner!

You got any pics of the car? I too have an '05(not stock
The issue with the headlight is probably a wiring issue from when they took out the flashers and such when they decommissioned the car. The LCM fix only works if that relay goes bad(which powers both sides).
The door speakers may have been hooked up to work with the police radio in the car and never hooked back up right, though some equipment installers don't use the connector and just cut wires so it could be an easy fix or could mean reconnecting cut wires.
With the mufflers, you still have a stock engine and the rest of your exhaust is still 2" so don't expect a huge change with just mufflers. I am using a full Stainless Works exhaust and it just sounds mean, yes it's a big cost but quality comes at a price. Some have used the OBX system(comes without tails) and been happy, it's a copy of the Kooks header and mid section of the exhaust up to the rear axle.
If you look up what can be done to a 2v 4.6L Ford engine, it can be done to yours, possibilities are endless as long as you have the $$ to support it.
You can get the 3.73 gears at many places, I went for the best price I could find and it was through an online Ford dealer(Tousley), do you want to swap in a locker?
If you are looking for performance parts for this car, go to ADTR.net for a great guy to deal with.
There are a handful of sites out there for the Panther enthusiast, check them out and search to see what kind of mods can be done.

Go checkout www.crownvic.net for many ideas you may consider.