Upper instrument pannel (Spedometer, Fuel gage,

Could be the stepper motor in the instrument cluster . GM instrument cluster had bad stepper motors . 2003 to 2006
How to repair GM Instrument Cluster Speedometer Gauge Stepper

Every light lit on the instrument cluster , could be data network problem . Do you know what a serial data network is , class 2 or GMLAN ? Hooking up a professional or factory scan tool to view sensor data to ECM - engine computer .
Fuel Gage
The instrument panel cluster (IPC) displays the fuel level as determined by the engine control module (ECM). The IPC receives a serial data message from the ECM indicating the fuel level percent. The fuel gage defaults to empty if:
• The ECM detects a malfunction in the fuel level sensor circuit.
• The IPC detects a loss of serial data communications with the ECM.
When the fuel level is less than a pre-determined value, the IPC illuminates the low fuel indicator.

What make , model an year vehicle ? If a GM vehicle 2003 to 2006 stepper motors in the instrument cluster are bad .
How to repair GM Instrument Cluster Speedometer Gauge Stepper

Check for a blown fuse under the dash. It will be marked gauges or instruments.

I didn't see an s15 in that model year, in my database?
If the speedometer works but the tach doesn't, I think something is wrong with instrument cluster?
GM has had a problem with fuel gage sending units. The sending units are not hard wired to instrument cluster, they send signal to pcm, the pcm sends serial data to instrument cluster, telling the cluster the gage settings.
It may be possible to use different size resistors in place of the fuel level sending unit, to see if fuel gage reacts properly to different resistors, if the gage reacts properly, then I think the problem is the fuel gage sending unit.

Put everything back the way it was and see if speedometer starts working again?
Newer instrument clusters, the gages are not hardwired, The cluster receives buss data telling the instrument what to do with gages and speedometer. Checking the speedometer/vss sending unit would be a thought. Hopefully, you didn't hurt the instrument cluster?
What is year--make--model?

If the odometer is analogue then it could be a broken speedo cable!

Dash board or gages

You may want to google "Dodge instrument cluster soldering" and get some images that are out there for procedure. Not a hard job, just have to remove instrument cluster and remove circuit board from it and flip it over and re-heat ( carefully ) some solder joints where plug from harness attaches.

replace the gages their malfunctioning ,check the wires for they are grounded.

Speedometer or fuel gage?

If speedometer which is bouncing around, it is likely a bad ground near where the speed sensor wire harness (which connects the speed sensor to the rest of the "network") exits the transmission housing. It's at the very back of the transmission (you have a 4T60E trans) to the left of where the right side half-shaft leaves the trans housing. Just look for damaged wires. If none, replace the speed sensor for $50-60.

If it is the fuel gage, the sensor is probably not "zeroed"--it's reading wrong, too high, and if it were to start at true "empty", it would read right. Thus, the gage is always reading a little high (maybe a 1/8-1/10th of a tank too high?). This isn't a problem until to stop, start, or turn quickly and cause the fule to slosh around in the tank and starve the in-tank pickup which sends fuel to the engine.

If it is the fuel gage, you should simply put as much fuel in as you can and see if the needle goes far above "F". If it does, note how far it went and then practice filling the tank when the needle is that same distance above "E".

Hope this helps.