Do the truck diesel fuel pump lanes also pump regular gasoline or do they only dispense diesel? (I have a gasoline truck + 36' trailer).

Diesel truck pumps only provide you with Diesel

Yes

It depends, if diesel fuel lane also has a separate regular gasoline pump, one could get the gasoline fuel.

No the diesel pump only dispense diesel

We fit in the gas pumps with a 37 foot motorhome towing a jeep wrangler, I am not sure about the diesel pumps having gas but you would fit at the gas pumps