First, I would say you need to determine your budget, as that will help determine the rest. If you can travel at any time of year (school calendars aren't an issue, work schedule isn't an issue, etc), I would say that late January and early September offer some of the smallest crowds. You can do a search of the WDW "seasons" and find out what times have the lowest resort prices.
Lodging costs can vary tremendously. You can rent an offsite condo or timeshare or vacation home for 2 weeks for a reasonable cost. You can rent DVC points to stay in a DVC resort on Disney property, or at any of Disney's many on-site resorts. Prices will vary from $100/night to $500/night, so you need to know how much you want to spend.
What all do you want to see in Florida? If you want to do Disney and Universal and Sea World, you could get a 10-day ticket for Disney, and 1- or 2-day tickets for the other parks. If you go in a warm time of the year, you can add the Water Parks Fun & More option to your Disney tickets and be able to go to the water parks several times.
You should consider getting a guidebook like the Unofficial Guide to WDW or the Passporter and read it so you can start to make decisions on where you want to go, what you really want to see and how to accomplish it.
And no matter what, even with 2 weeks at Disney World, you won't "see everything." I've been more than 25 times and still haven't seen or done everything.

That's what keeps me going back!