wiring for trailer hookup
 

I own a 2000 and 2009 mercury grand marquis. I read this morning that ford is thinking about not making anymore mercurys. Hard to believe since they are thick in my area.

My question: I want to add a trailer hitch to my 2000 mercury and need some insight.

The hitch I can do. The wiring I can do also but would like some advice before blundering into it.

The liner in the trunk is held in place with flat plastic buttons. The big ones unscrew but the little ones don't. Can I just pry the little ones off without destroying them? If I do destroy them can I get replacements? Is there another way that I'm missing?

The connection to the trailer is a flat plug with four wires.

There is a single bulb for brake, park and turn signals with two wires running to each bulb. Do I tap into all four wires or should the white wire be connected to it's own ground?

Thanks for your input.

they pry off. they will be destroyed. there are replacements. white wire to ground.