southwest的deal - 拉斯維加斯

看到southwest有hotel+flight的deal

但很怕自己解讀錯誤

Book a flight + hotel package of 3 or more nights at Wynn Las Vegas or
Encore, and receive $80 in savings (reflected in your package price). Plus,
receive 1 night free and an exclusive room upgrade.

Free night offer only applies to room categories that include "One Free
Night!" when booking your vacation.

Book: 4/2/10 - 4/15/10 by 6:00 p.m. CT
Travel: 4/7/10 - 8/31/10
Blackout Dates: 5/28/10 - 5/31/10, 6/4/10 - 6/6/10, 7/2/10 - 7/5/10
Five-day advance purchase required.

這是說假如我訂3晚的旅館 就只要付2晚的錢?
還是我訂3晚的旅館會送第4晚?

另外想請問版上有人訂過southwest的vacation package嗎?
我想知道訂了後可不可以改期?
網頁上的Restrictions都沒有提到這個部份...

謝謝~

--