If you have a VPI cleaning machine, then you are educated enough to know that there are special fluids for cleaning 78's. Disc Doctor claims to be safe for 78's and they pretty much know what they're doing. You will need to rinse with distilled or purified water. As far as value, like anything else, you have to track the websites and see what these discs are actually selling for, not just the asking prices. This takes time and patience. I did a quick search on Ebay and saw some Louis Armstrong 78's in the $5-10 asking range with no takers. So I would start with Ebay, just for the purpose of finding the jewels. Another option might be to find a collector to come and take the entire collection off your hands. Most record collections have a few gems that are worth money and the rest are of very low market value, regardless of the perceived value of the music. It all depends on how much time you're willing to spend researching. It's very time-consuming if you have a lot of records. Best of luck.