ges2mom, welcome to the DIS Camping Board.
I have a popup camper that sometimes we have put a tent with it. We go to the Fort about once a year (mostly around spring break but see my signature for specifics).
First the easy question: the weather is wonderful in October. Highs in the 80s, lows in the 60s. Here is the Accuweather link for Oct 2013 which shows that actual temps for each day and the historical averages.
http://www.accuweather.com/en/us/orlando-fl/32801/month/328169?monyr=10/01/2013
As far as advice, you can put the tent on the sand pad in the Tent, Full, or Preferred sites (those are listed in order of cost least to most). The Tent loops (1500 and 2000), the Full (1600, 1700, 1800, 1900), and Preferred (loops 100, 200, 300) vary depending on what location you want (near the beach, near the pool, etc), your budget, and availability.
Folks staying at Fort Wilderness sound like they spend more time relaxing and hanging around the resort than people do at the resort hotels. If you plan to be in the parks every day, you will miss the magic of the Fort. We spend one day in the parks for every day we are NOT in the parks and THOSE are mostly spent around the Fort. The Fort has lots of recreational activities not available at the other resorts plus some benefits like the upper end WDW resorts (view of the fireworks over the MK for example).
You sound like an experienced camper if you have a great tent so I say do it and you will most probably find you like it.
Bama ED
PS - come back at us with more questions or keep reading here to learn more.