Definitely doable in 7-9 days. We did it in a series of day hikes (see Trail Journal at
http://www.trailjournals.com/entry.cfm?id=197780 ). There are backpacker campsites, basically a table and open sided pavillion, access to lake water, and if I remember correctly a firepit. no other services. Use of these is free, and unreserved, so if someone else is already there you just share. There are several small towns you will pass through or near: Pahokee, Okeechobee, Clewiston being the largest. There are regular campgrounds in all three as well as other places arounds the Lake, you would have to pay at these. There are also small motels, and on the west side a fish camp that offers rooms and a bar (hiker friendly and a great place to stop for snacks and lunch on a chair!)
Depending on how far you want to go into town for groceries you could resupply at these, there are also gas stations with convenience stores you could resupply at, but that depends on your food needs.
You walk on the dyke all the way around the lake. On the east side of the lake they were doing dyke reconstruction for the past several years and may still be doing so. Some of these places were closed to access while they worked on them, requiring a road walk (on a not very wide road with no shoulders) in some places. For a lot of the walk there is a canal between the trail and the road, so once you have started on a section you have to keep walking to the next road access point to get across the canal. The maps should show where those roads are, just keep it in mind if you have seen a grocery or other place you wanted to stop.
Most of the hike is on a fairly level grass/rock surface, but the west side is a paved bicycle trail from Bell Glades to Pahokee.
I'd be happy to answer any specific questions, keeping in mind that it's been 3 years since I hiked it.
Janette