Starling is right that the fecals can get up there... you might end up having to do an office visit if you have never brought any of your reptiles in to that vet before, so they can establish a patient history. Even so an office visit will run only $40 or so, and if your gex are sick you will need to pay for meds.
Call around and get prices... don't just show up to the first vet you see. All vets should be able to perform a fecal flotation on reptiles, just as easily as they can on a dog or cat.
The only problem they may run into is identifying the parasite egg on hand, but they have books for that. If not you can find pictures of common reptile parasite eggs all over the net.
But like I said... the runny smelly stool sounds like it could also be a protozoan infection or maybe bacterial, so get a direct smear done as well.
And when you go to the vet, make sure they don't talk you into tons of extra things like bloodwork, etc...
Good luck.
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-Ross Payan - www.LeosAnonymous.com
Leos Anonymous
Ball Pythons, Red Striped Leos, and Screaming Fat-Tails