the first thing i looked up was
gîtes de france for paris; that's where we always find our vacation rentals and never a
soupçon of a problem. unfortunately they do everywhere
but paris.
i did a quick surf of
self catering+paris and the top hits looked highly reputable to me. my real concerns were price and availability as may is also a popular vacation period for the french (three-day weekends galore) but there were places available in may for between 300€ and €400 a week.
i also googled
fraude+paris with
tourisme,
location, with
vacances,
appartement... nothing. really, tourism is a major industry in france, and well supervised. so i don't think you should worry.
my wife and i have gone to paris a few times, we always find a hotel through
http://www.guidesdecharme.com/fr/ , generally try to budget at 80-100€ a night and the places have never been crappy... delightful comes to mind! still, for a 10 days a self-catering place will help you save oodles on eating...
al fresco will only get you so far!
as far as getting info from the embassy... i'm in the unfortunate position of occasionally needing their "services"

... just calling them on the phone is an experience! first of all, you have to give a credit card number just to talk to someone (15€ a call). for that, they can answer none of your questions and are snooty about it to boot. in fact it's probably the place in paris americans (well, everybody) get the
worst treatment!
when i was a big traveller i always used to go to the british embassies for help... they'd say "you're in the wrong place, the US embassy is down the street", and when i answered "yes, but they're always so nasty there", i'd get a big knowing smile and the help i needed.