It's not a difficult task. There is a petcock on the inside of the radiator or you can remove the lower radiator hose to drain it quicker. Just pour new coolant into the overflow tank to refill.
Here's the important part. Is your radiator fluid red or green. If Red, just go with the OAT coolant designed for your ISC. I use Peak Final Charge Global, but there are others such as Fleetguard ES Compleat.
If it's green, then you can replace it with similar green antifreeze containing SCAs. This type of antifreeze is a little more work because you have to keep replacing the SCAs that are depleted over time. Normally, this is a matter of replacing the coolant filter containing a shot of SCAs.
OAT coolants are definitely a lot less worry and I'd recommend changing over to an OAT coolant if you currently have the green type. You need to flush the system multiple times until you drain water from the system that isn't colored by the green antifreeze, then do a final flush with distilled water. Finally fill with an approved OAT coolant and forget about it for 8 years or a million miles.
There are lots of threads about changing to an OAT coolant so a search would find a lot of detailed information about it.
Here's a short video that explains antifreeze as it pertains to a diesel engine.
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