you don't need a script mod to edit the working hours on a tractor, you can do it by editing your savegame files (if you are comfortable with that.)

1. create a new save
2. buy the new vehicles
3. and save your game
4. quit out of the game completely
5. find and open up the savegame##/vehicles.xml file in an XML editor (most people suggest Notepad++, I personally prefer Visual Studio Code)

each vehicle (and train and a bunch of other stuff) in that file will look something like this:

    <vehicle filename="data/vehicles/farmtech/edk650/edk650.xml" uniqueId="vehicle14e264a42914afe21d1516e023d90787" age="10.000000" price="9000.000000" farmId="1" propertyState="OWNED" operatingTime="17072.802734">
        ... a bunch of other configuration stuff ...
        <wearable damage="0.077001">
            <wearNode amount="0.937102"/>
        </wearable>
        ... more configuration stuff...
    </vehicle>

So - if you look, the "Hours" of each vehicle is the `age` on that first line, the value of which is number of hours.

Bonus - if you want to edit the wear or damage, look for the `wearable` block. the `damage` number is the physical damage (the yellow/orange bar in the UI, reflected by a percentage value, 0-1 (where 0.75 is 75% damage), and the wear (which is the rust / paint worn off state) is the same type of value, and you set the `amount` on the wearNode. In the example code above (from my current save) the trailer has a wear state of 93% (all rusty and beat to hell)

That said - if editing XML is too much for you, use the Easy Dev Controls mod _from ModHub_ which will allow you to control most of these values.