Lcookster
It's true that Garmin doesn't make a dedicated chip for Winni comparable to the C-map chip with Bizer's map pre-loaded.
However, I just checked and their Mapsource US Recreational Lakes and Fishing Hot Spots - East CD (compatible with the 182) has a very reasonable chart of the lake, which, in combination with a hard copy of the Bizer map will be perfectly useable for your vacation.
You are correct in saying that the lake can a challenge to navigate; it's easy to lose your bearings among the islands.
It also has hard spots (i.e., submerged rocks) in unexpected places.
I believe that finding one may be what inspired the Bizer folks to start their map making business (see Bizer Rock on the map!)
Getting the software for your GPS is a good idea, but getting the Bizer map is a necessity!
Enjoy your vacation, and perhaps I'll see you on the lake!
Silver Duck