Have you tried Bitzi lookup (rightclick on filename in search result and choose bitzi lookup) If it's a popular file you will get some info there (quality etc. good or bad)

Also depending on what kind of mediaplayer you use. you might not be able to preview with it

If there are very few users that have the file, I would suggest picking another download, because it will take a long time and you can't be sure that you get the whole file

It's a win/lose situation downloading big file on dial-up + dial-up cost per minute/hour right. would it be less expensive to go out and just buy it, or can't it be bought?

try to do some calculating as to how long it will take, how much it will cost you and what it's worth