Just purchased a turtle that has never had any type of uv or basking light ?

I have just acquired a turtle that is eight yeas old and has never had a uv or basking light according to it's previous owner. Should I get one of these for my turtle or should I let It continue to live this way. I'm not sure introducing it to light will help or hurt the turtle after this many years. He seems pretty content and lively, I just want what's best for my turtle.