I would recommend not buying a microscope from eBay. There is a multitude of junk on eBay and even though the unit may look perfect there could a number of things wrong. Splitter mirrors broke objectives run through oil that are useless ECT. I recommended buying from a reputable dealer of new and used microscopes. I can buy from eBay because I have enough parts and know how to be dangerous.
With that said doing fecal exams are pretty easy
you will need a GOOD microscope with at least 100-400x power capabilities its not so much the power of the scope when doing fecal exams its the quality of the optics that really count
Fecal flotation media
This can be brand name fecosal or generic sodium nitrate (I think that’s the chemical I can’t remember right off hand)
Slides and cover slips
And the MOST important part is the education and knowledge to find and determine what you’re looking at. There are many good parasite reference books ect.but a good understanding of how a microscope is used and how to prepare the slides as well as identify the bugs is essential with out that all the equipment in the world won’t do you any good
please fell free to contact me off list
Mat Price