How do i know the waterpump is faulty...

Check engine light on ? What code ? There are many different (DTC'S) - diagnostic trouble codes that can set for knock sensors ! There all don't mean that you replace the sensor .
DTC P0324: Knock Sensor (KS) Module Performance
DTC P0325: Knock Sensor (KS) Circuit Bank 1
DTC P0326: Knock Sensor (KS) Performance
DTC P0327: Knock Sensor (KS) Circuit Low Bank 1
DTC P0328: Knock Sensor (KS) Circuit High Bank 1
DTC P0330: Knock Sensor (KS) Circuit Bank 2
DTC P0332: Knock Sensor (KS) Circuit Low Bank 2
DTC P0333: Knock Sensor (KS) Circuit High Bank 2

The knock sensor (KS) system enables the control module to control the ignition timing for the best possible performance while protecting the engine from potentially damaging levels of detonation. The sensors are located below each cylinder head on the engine block. The KS produces an AC voltage signal that varies depending on the vibration level during engine operation. The control module adjusts the spark timing based on the amplitude and the frequency of the KS signal. The control module receives the KS signal through 2 isolated signal circuits. The control module learns a minimum KS noise level at idle and uses calibrated values for the rest of the RPM range. The control module should monitor a normal KS signal within the noise channel.
Knock Sensor Replacement - Bank 1
Remove the exhaust manifold lower heat shield. Refer to Exhaust Manifold Lower Heat Shield Replacement.
Disconnect the engine wiring harness electrical connector (1) from the bank 1 knock sensor (2).
Loosen the knock sensor bolt and remove the knock sensor.
Knock Sensor Replacement - Bank 2
Disconnect the negative battery cable. Refer to Battery Negative Cable Disconnection and Connection .
Remove the engine oil filter. Refer to Engine Oil and Oil Filter Replacement .
Lower the vehicle.
Disconnect the engine wiring harness electrical connector (2) from the bank 2 knock sensor (3).
Loosen the knock sensor bolt and remove the knock sensor.

to Arkansas City, KS 824 miles

do the math -1galon =25 miles
824/25=33 by $3.50=$115.5

Faulty bearings in the waterpump, or waterpump frozen due to too weak of coolent/water mixture.

thermostat or waterpump faulty. loose drive belt for waterpump

check for low coolant, the cooling fan clutch could be faulty it is free wheeling all the time, when engine is hot fan clutch should have some resistance when you turn it by hand. if all is good, your ignition timing could be off,your radiator and engine need flushing out,you could have faulty water pump, a bad egr valve will cause engine over heat if stuck closed which will engine combustion temperature get hotter.make sure you have 50 / 50 antifreeze and water in coolant system too much water in coolant system will cause engine over heat.also radiator pressure cap.check all those things i told you see what happens.

The first thing is to check the coolant level, make sure engine is cold beefore removing the radiator cap, then start car with cap off and add as much as needed, this problem is not a bad thermostant, a bad thermostant would overhaet but would give heat, even if it was stuck open the heat would take while to get hot but then car wouldnt overheat, this problem one one of these problems, . low coolant or a bad waterpump, i have seen a few like this and the waterpump propeller rots away and coolant cant circulate, the last thought would be a bad head gasket but you would get heat when driving, so if coolant isnt low then waterpump is bad. hope this is helpful.

this is hard to say, not knowing whats wrong, it may be a bad waterpump or bad fan clutch,the fan clutch is the most common problem on these type of trucks,but could be the pump,to drive 25 miles i dont know,tell you what, open the hood with the engine off, grab the fan and try to spin it,if it binds up then its okay to drive, but if you grab it and move it back and fourth and theres alot of play then its a gamble but a would think it would be okay just keep an eye on the temp gauge, if it starts to overheat then shut it down and tow it the rest of the way,hope this helps,

You didn't list your engine size so please pick the applicable to your motor size:

Removal & Installation 2.8L & 2.9L Engines To Remove:

1. Lift the vehicle high enough to gain access to the knock sensor (KS) through the left front wheelhouse.
2. Remove the left front wheel and wheelhouse liner.

Knock sensor (KS) (A), Engine harness (B), Knock sensor (KS) connector (C)

1. Disconnect the knock sensor (KS) connector.
2. Detach the knock sensor (KS) from the engine block.

To Install:

1. Attach the knock sensor (KS) to the engine block.
   • Tighten the bolt to 18 ft lbs (25 Nm).
2. Connect the knock sensor (KS) connector.
3. Install the left front wheelhouse liner and wheel.
4. Fully lower the vehicle.

Your overheating problems can have several possible causes.
1) Airlock in heating system - solution - bleed air from cooling system.
2) Radiator blocked - solution - drain and flush radiator
3) Failed waterpump - solution - fit new waterpump
4) Engine thermostat stuck in closed position - solution - fit new thermostat
5) Electric cooling fan (if fitted) failing to operate - solution - check fan, fan operating switch, all wiring and connectors
6) Not enough coolant in system - solution - check and top up to required level. Also check all hoses for sign of leakage.
7) Faulty temperature gauge giving incorrect reading.

Sounds like your car is overheating, do you have any coolant leaks? If you are leaking coolant possible causes are radiator and or hoses or waterpump. If you are not leaking coolant you probably have a faulty thermostat that is stuck closed and not allowing coolant to circulate into the motor.

Hope this helps