I know this
https://www.jameco.com/webapp/wcs/stores/servlet/Product_10001_10001_120539_-1 isn't good enough, but it can give you a place to start. I have used it for both a speed control and a shutter solenoid driver. The motor I used for the speed control whined using the controller.
Note: I like presenting stuff without justification to provide a "basis" for a design even if the idea is quirky.
It does include soft-start.
There are a few problems with this application:
1) Engine compartment (Environmental)
So, you might have to use a diecast aluminum case with an "O-ring" seal. Another possibility is doing it in two pieces.
2) The automotive electrical system.
Transients of -200 to +50 are common. You have to protect against that.
3) You may have to reduce the electrical noise made by the device into the 12V system
4) You have to be able to handle the short-circuit current, at least for a short time.
So, te 25A is probably while running. the surge might be considerably higher
5) The Velleman kit gives you a place to start and you have a scematic, so you have these problems to solve.I'd try to get it to work with the ignition off and without paying attention to environmental issues first. You MUST add a negative voltage and positive voltage clamps. Transorbs and a 1N500x diode with a PIV greater than 200 V should work with a fuse. It would be handy to know the DC resistance of the motor. Measuring that might require a 4 terminal technique. e.g. Current through the motor and voltage across it at a low voltage.
1. Frequency of operation
2. The FET output should be selected and properly heatsinked.
3. Add the OVP and transient protection.
Now work on environmental.
I'd suspect that the case of a large diecast Aluminum box will work as a heatsink. A finned sink could also be added.
The magazine NutsandVolts always has PWM modules for sale.
I did some searching (minimal) and found this:
https://www.avayanelectronics.com/Products/AE-7960/ae-7960.html Note, that it says "proper heatsinking".