All cars have problem as they get older, just like we do and Electronics do not last forever even though we would like them to.
If you sale your Monte Carlo and buy another car you will pay WAY more than if you just fix what is wrong with your car. People are so dumb some times.
They have this "THROW AWAY" mentality.
I have a 2002 Dale Earnhardt Edition Monte Carlo with a few electrical problems. The headlights don't go on some times. All I do is turn on the 4 way flashes and move the turn signals left and right and the headlights go on. I believe it is the HAZARD switch that is the the reason. It is a switch that almost never gets used and the contact get dirty, especially if you smoke in the car. Just push the switch 8 or 10 times once a month and work the contacts the you won't have this problem. As for the dash lights not working, 8 out of 10 times it is going to be the Body Control Module (BCM). The BCM control a number of things. It controls : Interior light system, exterior light system, Headlight system, remote keyless entry system, shift interlock system, anti-theft system, trunk, tailgate, fuel door systems, door lock system, Air conditioning system, Rear window refogger.
Here is a break down of what the BCM controls
1) Courtesy lamps
2) Park Lamps
3) Keyless entry System
4) Fog Lamps
5) Ignition Voltage
6) High Beam headlight Relay
7) Horn Relay
8) Backup Lamp Relay
9) Auto Trans Shift Lock Solenoid
10) Security System
11) Instrument Lamps (includes steering wheel sw lamps/ door sw lamps/ radio and A/c - Heat control Lamps)
12) Trunk Release Relay
13) Trunk Ajar Sw.
14) Daytime Running Lights(DRL) Ambient light Sensor
15) Door Lock Control System
16) Interior Lamps (dome and under dash lights)
17) Traction Control Switch
18) ABS System
So it you have a problem with any or a few of these system you need to check the BCM before you start pulling apart a wiring harness.
Remove the panel under the dash, look up ! between the steering column and the E brake and you will see an Aluminum brace, the BCM sits above the brace, it has 3 connectors on it (pink or samon) blue and white. Remove the 3 connectors first(if you try to remove the module with the connectors on you will never get it out) then push the module toward the front of the car and pull down. After you have the module in your hand plug in the connectors again. for no dash, steering wheel A/C-heater lights or door sw. lights check connector "1" wire B11(gray wire), if there is no voltage then the module is bad.