Why would I be getting a puddle BEHIND the DRIVER'S side front tire. With pressure on the system coolant runs out of the inner finder well on the drivers side. The black matting behind the inner finder (at the door opening) is soaked. Could this be the heater core all the way over here? If so how do I change it. Read the directions from Haynes but doesn't seem to be for my car. Any help would be greatly appreciated!

Could be the heater pipes that run along the rear of the motor. They do rot out over the years.

Heater pipes? Not sure what exactly I'm looking for. How do I access them for inspection / replacement?

The heater pipes run along the rear head are black in color and are a PITA to get to, when I replaced mine I had to disconnect my rear motor mount from the frame and use a floor jack to tilt the motor forward

I would also inspect your coolant crossover it runs from the front head to the rear head on the driver side of your motor just under the TB.

If your car is still equipped with dex cool look around the motor compartment for a white crust this indicates dried dex.

Read the directions from Haynes but doesn't seem to be for my car. Any help would be greatly appreciated!

Haynes will not even give you the right procedure to change a tire for Cadillacs. They're sketchy at best for normal cars; I've gotten a couple tidbits out of the Haynes for my daughter's Jeep. If you want to work on your car invest in a Factory Service Manual (FSM). Try eBay or www.helminc.com or subscribe your car to alldatadiy.com