Yes you need the DLC if the mod uses DLC parts. I'm not sure if that means you just wont be able to buy the DLC replacement parts for a car or if the car will actually not show up in-game though.... Maybe someone else knows.....

There are plenty mods in the workshop that don't require paid DLC. The page for the mod will display what DLC if any is required.

thank you so much

P.S. If you enjoy this game then, I highly recommend going ahead and getting the Platinum edition on the next sale--it'll reduce in price in your cart for the base game since you already own it as well with any individual dlc. I personally had bought base game then dodge dlc and later decided I wanted it ALL and bought the whole pkg in a sale at which time it reduced price for already owned content. So, it's a great deal then.