would a '03 dakota cd players fit in an '01 dakota with a cassette player.

No, because the connectors on the back of the unit don't match up. If you do have an '03 CD player, you can go to either the dealer or to a place like soundadvice and ask for the adapter. The new adapter, revised in 2002, has a single 22-pin connector while the old style has two 7 pin connectors.

thank you thats all i needed to know.