Since your receiver is older, you will need to connect the video outputs of the DVD player direct to the TV and the audio outputs to the receiver to hear the sound via the receiver. If you go the other direction, connecting the audio to the TV directly and use the optical to the receiver from the TV, you will most likely get stereo output only since analog inputs are limited on most newer TVs.
If you get a Blu-ray player with HDMI, you will be able to use the optical out from the TV to the receiver, providing the receiver has optical inputs.