I think that the analog potentiometer that its going to replace is 30 Ohm?
What makes you think that? It is a very very low value for a pot.
That chip has a minimum working voltage of 10V, so you will have to find a digital pot that can stand that much. You also have to prevent that voltage getting back into the arduino so you need to buffer the signals with transistors or opto isolators.
30 ohm is of course a typo, I meant 30 K ohm? I have measured the resistance of the pinhead-sized pot and it goes from ~ 5 K Ohm to 30 K Ohm.
The problem is that the circuitry with the MC33035 is covered in some material, I don't know if its epoxy or what it is, but it makes it pretty hard to figure out if the controller is directly connected to the outgoing wires etc.
And I currently don't have either an battery or power supply that can deliver the 24 volts required , so it would be possible to use an multimeter to check, the outgoing wires.
But in think I measured the voltage to be 5V and the current to be extremely low on both the fwd/rev and throttle, when I did the initial studies (and had a battery), but that's over 1-2 years ago, and I'm not 100% sure..
And I don't know if that's low enough to be able to control it via something like the AD5206.
The problem is that the circuitry with the MC33035 is covered in some material
You didn't say that in the first place, I assumed you just had the chip, not a full unit containing the chip.
The actual size of the pot doesn't matter as it just acts as a potential divider with very little load. What does matter is what voltage is on the 'hot' end of the pot as that is what your digital replacement will have to cope with. You need to measure it.