Most likely the fecal test sent out was a stain test for giardia and I think if the stain test is done it is fairly accurate so you can probably rule out giardia.
Coccidia is spread through cysts in feces that are ingested. Coccidia is a strange parasite because a dog can have it, but it not be activated until stress or their immune system is compromised by another illness. People often take their dog to be boarded then come back with coccidia and believe the dog was infected in the facility (which maybe he was, but most likely he already had the cysts dormant and the stress caused them to activate).
There's really not a medicine that kills the parasite it only stops reproduction. I've heard of puppies having to stay on Albon for up to a month to finally get rid of it. If he did have it he can reinfect himself through his own stools - so you have to follow strict hygiene cleanup of poo. The fecal tests are not always accurate because every bowel movement does not shed the cysts (eggs) so they usually recommend 2 or 3 tests given on different days or they just go ahead and put them on Albon until the immune system can overtake the parasite. That's why I would talk to the vet about boosting the immune system while treating with Albon.
Here's a complete link to an article.
http://www.peteducation.com/article....&articleid=726
P.S. I would think you are wise to make sure he is 100% healthy before using any anesthesia, especially since anesthesia is known to weaken the immune system which might already be compromised.