DVD/VCR Combo

First let me start out by saying I'm a certifiable techno-dummy. That said, let me explain my problem. I have a Zenith combination DVD recorder/VCR unit that is about 3 years old. The DVD player started skipping, and discs were unwatchable. I thought maybe the laser needed cleaning, so I bought a disc cleaner. Most of the time when I inserted the cleaner disc I got an error message. The couple of times I got it to work didn't seem to correct the problem very much. I tried to take the cover off and clean the laser with a little acohol, but the screws that hold the cover on are practically welded on. I think maybe it's time for a new one.

My TV is analog with rabbit ears. As preparation for the switch to digital, I have a converter box for it, which I haven't installed yet. I have my eye on a Panasonic DVD/VCR combo with ATSC tuner. My understanding is that recorders without a tuner will be useless after the switch to digital. But do I really need to have a tuner if I have a converter box? What is a tuner, anyway? And what is an "up-converting" recorder? There is a big difference in price between tunerless recorders and up-converting recorders. I'd like to buy the least expensive type that will still work for me after the switch to digital. Any answers and advice is greatly appreciated.