Those old, thick 78s can be especially valuable if you have the key artists. Donan said he is looking for early country music 78s, and others with examples of early jazz and novelty records.
Slicks are the art prints that are used to create album covers.
The original collector of the 57 slicks considered selling them to a hotel in Las Vegas, and that is still an option if the starting price on eBay is not met. Thousands of record auctions are posted on eBay. Maybe, but the odds are not good, because the priciest recordings must be in the best condition, and records are easily damaged by heat, moisture and improper storage. Even if they were stored correctly you must wonder how they were preserved during their useful life. Yes, it is a gamble.