Pioneeer 420 H won't read discs?

My well-used Pioneer 420 H will not recognize when a disc, either blank or recorded, is inserted. It displays a message "no disc" or, "cannot read disc". It still plays the content on the hard disc drive, but will not play or record any dvd. Any ideas what is up with this?
Pioneer wants me to ship it to their service center with a money order in the amount of $75.00 US as an "evaluation fee". Shipping will not be cheap, and repair may be expensive. Is there any point in proceeding or should I trash the unit?