You remove heater core in doge neon by smashing the windows then taking off the doors so you can get th the heater core then you get a crowbar and rip it out (if this destroys your dodge neon then your car isn't a real dodge neon).
There is no difference besides the badge on the car. I had a 2001 Plymouth neon and now have a 2002 dodge neon and the only difference between the 2 is the badges and the grill. and the grill changed with the 2002 model.
You can access the middle brake light from the inside of your 2000 Dodge Neon cargo compartment. Remove the brake light wiring harness. Remove the brake light retaining bolts. Reverse the process to install the new brake light.