LG RC797T Won't read disks

I have an LG RC797T DVD Recorder/VCR combo which won't read any DVD that I insert into the machine. It will attempt to read the disk, and then say that it doesn't recognize the disk, or that there is no disk at all. The only thing that sometimes works is when I insert a blank DVD-R and dub from VCR to DVD. I've read many similar compaints about this machine online, and the major problem seems to be poorly manufactured lasers within the DVD drive. I was wondering if it is possible to replace the DVD drive and keep using the unit, or is it a better use of my time and money to just junk the thing and buy from another company?